It might be problematic in countries where certain kind of sexual orientation is punishable even with death. If you don't live in those countries, then I don't see much problem with GA in these sites as well.
Are you claiming that in those countries there have been cases where people are identified and rounded up with some mass sweep identification by online viewing habits?
I was recently googling friends' names and looking at the results from find-people sites. It's already creepy enough that they have "related to:" and then a list of family members of that person. But the most recent concern was one site already has a "reputation score" like china has already implemented. I checked a few friends who had criminal convictions and, voila, their "score" ranked lower (and of course you can pay the site to remove your entry or whatever, aka a racket). Porn viewing could easily be ranked into the "score" in a negatively-impactful way and lead to job/social discrimination.
Do I care if Google & Facebook track my viewing habits? I'm not sure I understand what the potential harm to me might be.