I'm going to be completely blunt and say that it is always my assumption that people are watching shows "for the girls". But only because I consistently see people talking about watching shows for the girls. Even in seemingly innocent shows like New Game, it's all about how cute they are, or in something sci-fi/fantasy like Re:Zero, it's all pictures of Rem. People don't even seem to realise the Monogatari series is satirising the whole harem thing, and even when this gets pointed out to them, it still seemingly doesn't click that maybe Nisio Isin is mocking them. Obviously it happens with stuff like Mr. Osomatsu and Free! as well, but it always seems to be more overtly treated as shallow and objectifying when that audience does it.
I probably am being unfairly presumptuous about certain fans/shows, but I don't think it's without good reason. Though, I probably do equally questionable behaviour with the shows I watch too. I guess it's hard to see how any fanbase or people grouping comes across if you're part of it.
I think it's also a case where fans talk about things in a certain way that wouldn't be interpreted the same by those outside of their group (and even within their group, at times). "Cute" can refer to physical attractiveness but it can also refer to different types of behaviour or personality. The appeal can be sexual but that's not an inherent aspect of it. To be fair, I think "cute" might be one of the least precise and most open to interpretation words there is, I tend to use it loosely anyway and maybe that's unhelpful. Along similar lines, the term "moe" has been significantly reinterpreted and can mean very different things to different people. That's a particularly interesting case since people who use the term probably don't mean it to have any sexual connotations while those who wouldn't use the term may be more inclined to assume sexual connotations.
I think cases like the pictures of Rem from Re:Zero are probably related, they're kind of part of a shared culture of the group and they might mean something different to those inside the group than those outside would think (or they might mean exactly what they would think). I guess that sort of thing can also be used as a way of showing belonging to a particular community so that meaning may be more important to some than any more direct interpretation of their activity.
It probably also doesn't help that people can sometimes "play along" with the reputation of a group they're part of in a way that can exaggerate how accurate that reputation might be.
At the end of the day, I think the key is to avoid making assumptions about individuals based on the groups they happen to be part of. Groups may have general tendencies towards particular features and there may be evidence to suggest this (though the evidence may be deceptive) but groups are ultimately made up of individuals and individuals tend to be complex and non-standard. Even when people do meet certain expectations for a member of a particular group, that's still only going to be a part of their personality.
I guess that's all rambling a bit, but to try and turn it around to being more relevant to the topic, I suppose I tend to think that it's the responsibility of people outside of groups to avoid making assumptions and to engage with members of the group if they want to get an accurate information on that group. I'm still not sure that's entirely relevant but it's maybe the best I can do.
Just to add another aside, I checked my comments on New Game! and I notice that I only used the word "cute" twice. That was in the context of "cute girls doing cute things" and only in comments on the first episode. I could easily have used the word "cute" more often but, looking back, I thought it was kind of interesting that I didn't.
