I do my best to follow the general forum rules about not bringing up politics or religion, but if someone posts something which is on the borderline of these issues, and makes definitive statements which I disagree with, I sometimes feel compelled to not let their assertion stand without comment. The recent climate change thread was a case where this occurred, and I felt that it would be unethical of me to let some of the other posts go by with no argument.
These forums should be about PCLOS, Linux, computers, and technical matters, as far as I'm concerned. Off-topic, lighthearted content in the sandbox is great, as long as the areas of contention (politics, religion, and the like) are avoided.
As far as I'm concerned, locking or purging troublesome threads is completely reasonable.