Oh My ______ (Insert name or non-name reference to your acceptable deity. Alternately, name or refer to your favorite idolized musician or sports figure.)
IMHO...
There are only two topics of any lasting importance. How we relate to our creator and how we relate to our fellow man. Religion and politics.
NT or ND, many of the problems we have touch on these seminal issues. They emerge all over the place. What now? We're going to task the site staff with hunting down and obliterating any post on any thread that touches on religion?
I'm convinced we're made of nobler stuff than that.
It can be necessary sometimes.
It really depends heavily on the forum as a whole, and the purpose/function of that forum.
There's another forum I frequent and in fact moderate, which is related to an indie dev I've contracted with a few times. There's a rule there, which I will enforce with unflinching ruthlessness, which is: No politics. Period. If a political topic pops up, or if a non-political topic GETS political, I lock it. It's that simple.
WHY, you ask?
The official reason is that the developer as a whole... who DOES function as a business selling a product (the games they make) doesnt want to be seen as being linked to ANY specific political thing at all. They dont want the potential customer's purchase decision to be linked to "oh this developer supports THAT guy, huh?". The decision to buy or not should be about the product being considered, nothing more. So.... yeah. No politics, period. Every now and then someone on the forum expresses a dislike for that rule, but... bloody tough. It is what it is, and it is there for a reason.
Okay and the other reason is to avoid ridiculous flame wars, as political topics have a tendency to be quite flammable on the Internet. And I will admit that reason #3 is my utter loathing for the topic as a whole.
My point though, is that there can be genuine reasons for even an entire forum to avoid certain topics, and those reasons are, in the end, entirely up to those who own/control the forum. Agree or disagree, it's their decision for their reasons in the end.
NOW, that all being said, I must also say in response to the OP... there's little point in complaining about it either way, from the point of view of a general "user". Just... dont click on the things you dont like. It's the freaking Internet... if you cant manage to avoid doing that, you will soon be driven to absolute madness. I mean, seriously, "just ignore X thing instead of reacting to it" is like Internet Usage 101 here.