Feels like the opposite to me - NTR fans have repeatedly gone into several harem game threads I follow and posted over and over that the game should have NTR (even after the dev has replied clearly that NTR will not be a part of their game). So over time harerm fans have gotten quicker to proactively shut that down as a reaction to that trolling. (Maybe harem fans go into NTR game threads and do the same thing...but I doubt it because most harem game fans don't want any part of NTR games.)
In fairness
both sides probably have immature jerky posters that the decent folks on both sides have no control over, so we probably all just have to suffer.
To your point that NTR games can have harems I completely agree because
NTR fans are who those games are made for. The opposite does
not work, though, because harem games are made for harem fans specifically, and most harem fans are
not into NTR and don't want to see it in games specifically made for harem fans.