What a daft thing to write! How can a message board with hundreds of thousands of unconnected random posters hate anything? I've seen posts fervently pro ensuite and fervently anti though, so it is true that (like shoes on or shoes off in the house) it is a theme that can prompt strong feelings which seem disproportionate. I think in both cases it's something that people feel on some level says something about them personally. If a subgroup of people you viewas peers seem to jusge ensuites or taking shoes off in the house negatively, people who have chosen those things for their houses feel judged personally and want to defend and justify their choice to someone (and of course the same the other way around).
I don't like ensuites because most of the ones I've been in are cramped and windowless, which I find unpleasant. They usually only have a shower. A large ensuite with a bath and seperate shower and agood sized window would be a nice thing but rare IME.
I very much dislike having other people in my bedroom and would dislike any set up involving being expected to let anyone else walk through my bedroom to use an ensuite bathroom - ensuites bring the problem that different households have different etiquette and some people expect to use the nearest bathroom including ones reached by walking through a bedroom, while others see ensuites as off limits except to the occupants of the attached bedroom.
Some new builds only have ensuites and no guest or family bathroom meaning walking through bedrooms is unavoidable.
In any event I would hate to have to clean four ensuites rather than one big family bathroom and one downstairs toilet.