Because the responses look to me more like conditioned reaction than something considered.

If it is, as you hypothesise, rational to avoid even slightly politically-tinged discussion to this degree, then that greatly reduces the hope of raising the sanity waterline. Because very few problems people want and need to solve are going to be free of such a tinge.

As I've noted elsewhere, this doesn't mean I think we should dive headfirst into it on LW. I don't have a handy solution. But I do think it's a problem.