A big problem - and perception - with such threads (which leads to supporters of either "side" feeling they are picked on and those on the other side are given carte blanche) is that people focus on the topic of the thread rather than the nature of the thread.
If it's a negatve thread, it's far more likely to be one those which erupt into argument. An "I love X" thread is almost always OK, but an "I hate X" thread is more likely to go downhill.
And of course, with a new game on the block, your'e gonna get a lot of "I love the new game" and "I hate the new game". Unsurpisingly, the former tend to be peaceful, and the latter tend to be acrimonious; and therefore they attract moderator attention. Conversely, you get few"I hate the old game" threads, and so less moderation on that side of the coin.
Then of course, you get folks saying "the mods moderate those who don't like X, but not those who like it", which is blatantly untrue (we truly couldn't give a flying crap which version of the game you like); the truth is that the mods moderate those who act in an antisocial manner, and the "I hate X" threads tend to attract such posts.
So the issue isn't of a difference of opinion in edition preference; it's of the
delivery of that opiion. It's the difference between "I hate
4E and people who play it are idiots..." and "I love 3.5, and here's why..." (exagerated generlized examples, obviously, but they serve to illustrate the point).
In short, just being polite and friendly, whetever you point or opinion, will pretty much guarantee you're OK.