Consider it like a ban. The contentiousness is the point, not the subject matter per se. It doesn't have to be politics or religion necessarily - those are just the two subjects long considered most inappropriate for tabletime discussion.
Few consider this traditional recommendation disenfranchising, or a denial of peoples' individual special snowlake natures. It's just a necessary rule imposed to keep the peace, based on an understanding of how people tend to behave. (And by "tend to", I mean, of course, "basically always".) And when people seem to be voting against discussion of a subject here, you should take it the same way.
Think of it as you might a ban on discussing religion and/or politics when dining with people you don't know especially well. Less an attack on MAH FREEDMS, more a simple means of keeping the peace. You may complain that this will give rise to nothing but an echo chamber - and that's possibly true, but I fail to see how it's any worse than the alternative ;)