So stop cluttering your front page with it. This is far worse than sponsored posts, and you're probably not even getting paid to post the political junk. Sponsored posts can at least be justified by the fact that a site needs money to operate.
There are two reasonable stances that a site with an active community forum can take on issues. One is to allow discussion of an issue, with only some guidelines prohibiting things like personal attacks. The other is that discussion of the issue can be banned entirely. The latter is the site's official rule for politics and religion, for example. The former is generally the case for gaming issues that are the core focus of the site.
The complete ban on discussion of some issues is completely reasonable, provided that it is even-handedly enforced. People learned in the early days of the Internet that certain hot-button issues tended to lead to flame wars. Furthermore, they'd tend to consume the site and drive out discussion of whatever else the site was about, in a manner roughly analogous to Gresham's Law. But at minimum, an even-handed ban on discussion of particular issues has to include a ban on making "news" stories advocating a particular side of such issues.
There are some issues the straddle the line between politics and gaming, so you get semi-political issues with an obvious gaming connection. This site's traditional approach to such issues is to allow comments for as long as they stay civil. If the comments turn into a flame war, then lock the thread, delete some posts that went too far, and maybe ban a person or two who went way over the line in a full-on flame war. This has worked pretty well for quite a few years now.
In order to do it right, such moderation has to be even-handed. It's no good if a moderator allows wildly over the top and incendiary posts by the side he personally agrees with, but bans measured, civil disagreement with his own personal opinions. You have to allow civil posts on both sides, while stepping in to delete posts and ban people for blatant personal attacks regardless of which side of the issue they're on. This is not trivial to do, as it's human to tend to be more offended by opinions that you disagree with than by those that you agree with. But you'll get much closer to doing it right if you're at least trying to do it right than if you're treating moderation as if disagreement with your own personal opinions is the primary bannable offense.
That's basically the opposite of what is going on now. Instead, we have the spectacle of the site banning people for questioning the new political slant of the site in ways that are literally less incendiary than official front page posts that are marked as "news". That's extremely poisonous to a community, and exactly what you cannot do if you want the site to thrive as it has in the past.
I can understand making a post, realizing that it was a mistake, and locking comments on that particular post. But if that's the explanation, then stop making more posts like it. Mistakes are not a field of characteristic p, so adding more of the same mistake doesn't fix it.
How to fix the problem really depends on the reason why it is happening. I see three real possibilities.
1) The new ownership bought the site wanting to politicize it and approves of the political junk that you're posting. If so, then you can't really stop a man from burning down his own property. In this case, the site is going to fall apart and there's not much that can be done to stop it. I hope this isn't the case, but no human institution will last forever.
2) This is a principal-agent problem. The site's owner wants it to be a successful site about MMORPGs, and doesn't want it to be used to advocate particular political views, knowing that that will chase away everyone who would otherwise be interested in the site but disapproves of the political slant. Instead, it's a rogue admin who has decided to use his privileged access to the site to push his own political views and ban anyone who disagrees, knowing full well that that isn't why he was given admin privileges. In that case, the solution is to permaban the rogue admin to banish him from the site, unban the people he has banned for disagreeing with him with a profuse apology for the abusive moderation, and move on.
3) The person who is politicizing the front page of the site doesn't realize what he's doing and how destructive it is. Part of becoming a mature adult is understanding and accepting that some people disagree with your strongly held personal opinions, and that that disagreement with you doesn't make those people evil or delusional. Some people aren't there yet and probably shouldn't be given moderation responsibilities, but if this is the case, then I would appeal to you to consider the opposite scenario. Would you want to hang around on a site that posts official opinions that you disagree with and bans anyone who states that they disagree? If not, then why would you expect anyone else to want to? A community for people interested in MMORPGs has a much larger potential target audience than one for people who are interested in MMORPGs and also agree with a particular collection of political opinions. Even if you can survive for a while as the latter, if it's legal to mandate one thing as the site's official political viewpoint, then there will always be the temptation to add more things to the list. As the list of officially endorsed political opinions lengthens, the set of MMORPG gamers who agree with all of them will inevitably shrink.
On the general principle of assuming good faith, I hope that (3) is the explanation. Everyone was immature at some point in the past, and it can be a blessing to have had the chance to make your mistakes and learn from them in obscurity, rather than being given enough rope to hang yourself with publicly before you're ready to handle the responsibility.
And no, a political opinion doesn't become gaming news just because someone in the gaming industry said it. You can find people all over the map with their own political opinions. Cherry-picking the opinions that you agree with as the ones that you'll post while prohibiting criticism of those opinions and using that as a way to advocate your own opinions while pretending that you're not is an old, cynical trick that everyone sees right through--and hates. So stop it. Please. Either stop posting political opinions on the front page or else open them up to disagreement rather than banning anyone who disagrees.