I don't really know what Harem Anime is (besides, yanno, knowing what both of those words mean - I mean I'm not familiar with the genre) so I'll skip that and just address porn.
First, porn isn't inherantly sexist. Sexist porn is sexist, non-sexist porn isn't. It's kinda a little worrying that that needs explicitly mentioning. Second I dont understand - and I suspect I never will, this might be an unsurmountable wall between us - how you can say "Yeah, its sexist but so what". Are there - and this is intended as a genuine question - things that you think "yeah, they're racist but so what"? Because, I dunno. Euw.
I probably have a poor internal definition of the word "sexist" then, and end up conflating the terms sexist, sexualized, and sexy. I'll have to come back later on this point once I've thought things through more.
1)I don't honestly view this as an important line of inquiry - the onus is on (hypothetical) you not to be a pig not on (hypothetical) me to call you on it. The analogy is with victim blaming, though I'm not suggesting this is anything near the most extreme example of that.
No, the intent wasn't for this to be victim blaming, the intent was just to set up a hypothetical situation where he could wear the shirt if no one was offended by it, but had to remove it if someone was offended by it. The thought exercise is basically the idea of, "if this literally does not affect anyone in a negative way, is it still bad?"
2)Again, I think its the wrong question. If everyone were treated equally, then noone would be wearing a shirt like that. I see it as a self-refuting question.
I could easily envision a world where women in science fields (and everywhere else, really) are given the same opportunities, the same payment, and the same recognition as men in the same fields, and still see a few people deciding to express themselves by wearing a shirt like this. Alternatively, if everyone were treated equally, he could be wearing this shirt while a female coworker wears a similar shirt, only with half-naked guys plastered all over it.
To clarify my question though, I'm specifically saying that the hypothetical world isn't necessarily one without sexism between individuals, but it is one free of sexist biases when it comes to main issues such as employment opportunities, wages, and so on.
3)Sorry, I'm a little unclear on precisely what this question is. I'm goning to answer "Where would the line be drawn" as my best guess but if I've misunderstood then sorry.
I'm always wary of "where is the line" type arguments - they can generally be answered with "the line is drawn in the appropriate place, obvi". In this case, well, what do you think? Do you for one second think those two positions are the same? Is this really a source of confusion? I'm sorry if I sound incredulous and it was a real and genuine question but it...I dunno. It really doesn't sound like something you actually see as an issue.
I know this can be a silly question, but I'm building towards a point here, and I'd really rather not put words in your mouth in order to make that conclusion. My point is, however, that there can be a lot of shirts, posters, etc that are offensive to a small group. As I said, a religious person may find offense that their coworker is allowed to wear a Harry Potter shirt, thinking that it marginalizes them. Heck, the person with the Harry Potter shirt could be atheist, and think that the religious person's cross necklace and shirts with religious messages is offensive to him. Or heck, if you don't think that's offensive enough to cause problems, what if instead of a Harry Potter shirt, it was a very anti-religion shirt? Would you say such a shirt is also not appropriate for work, and if not, why not?
One more question that I thought of, though this is going off on a tangent and isn't related to the point I'm working towards with the other three questions. In some video games, especially MMOs, it's not uncommon for a few pieces of armor to look like normal, full-body plate mail on male characters, but end up incredibly revealing on female characters. Personally, this is one of those things I'd classify as "sexist, but not a problem", but again, my definition of sexist is probably not right. However, there is at least one game where the highly-revealing female armor is equally revealing male armor - a chest piece that can be aptly described as "boob plate" on a female character, when worn on a male character, is little more than a few leather straps across his chest connected to a tiny piece of metal "armor" that's only slightly bigger than his fist. Would you consider such armor sexist, seeing as how it is equally revealing and impractical on both sexes?