Although the "but why does everything have to be about sex" complaint automatically puts flames on the side of my face regardless of who or where it comes from.

ME THREE. There's a reason m/m and f/f ships get that reaction so often and while it's technically possible that someone who says that could be a perfectly innocent non-homophobe who objects to m/f ships with the exact same frequency, from my experience in fandom and real life the chances of that sentiment being expressed from a non-homophobic place are... not high.