I think the best way to avoid falling into that kind of trap is to learn to dissociate between a value one believe in, and a discourse/action done in the name of that value.
It's perfectly possible to agree to one without agreeing to the other.
People who haven't yet learned this[1] tend to think that disagreeing with the latter also means disagreeing with the former. Worse, they might believe that not personally sharing/believing a value constitutes an attack on this value. And since one's identity tends to be tied with one's deeply held values, it constitue an attack on them or on their peers as well.
The important point is that good people might do it in good faith, out of naivety. In the Opal thread, however, I believe most of the 'Twitter army' that came to +1 the CoC uses it as a rethorical trick, out of self-righteousness.
[1] And I honestly believe that most early twenty-something tends to fall into that category, especially the most politicaly or religiously active ones.