I don't "dislike" all Cho-haters. I understand if you "hate" her because she kept crying. Honestly, before the GoF movie came out, I was pretty indifferent to Cho. I did not love, like, or hate her. She was the "take it or leave it" character for me because I believe I (as the reader) did not get to know her well enough.
In reality, it was most/all of the Cho-haters' comments that actually started my empathy towards her. I agree, she cried too much. But we only know that because of the few times Harry actually spoke with her, he caught her at a weak moment; and Hermione told him that other girls had been saying she was crying "all the time" too. Well, she is a teenager - they all are - and as a "teenager", there could have been a tad over-exaggeration. Basically, she was depressed. It's understandable.
In the books, I hate to say this, but it seems as if Dumbledore showed favoritism towards Harry and his friends. Maybe because I (as the reader) did not get to see him interact with many other students (not even in passing). I see it - and I am extrapolating - that he did not tell Cho what had happened. Naturally, he spoke with Cedric's parents and Harry's family (by this, I mean the Weasleys) but I don't believe he spoke to Cho. It was (1) Cedric was murdered, (2) school is out for the summer, (3) go home. So, she had questions still.. questions that went unanswered during the summer... and she went to Harry for the answers. I think she was "numb" during the summer, that reality didn't hit until she started getting ready to go back to school. (Perhaps it is because I went through a "numbness" myself when my ex-first-boyfriend/first-love broke up with me before the summer, and I didn't see/talk to him at all during the summer, and only saw him again when school started again. For me, the break-up didn't sink in until we saw each other again and I saw he had moved on with his life and I realized I hadn't.)
Back to "hating" and Cho-haters. Yes, I agree she shouldn't have dated Harry when she wasn't over Cedric. But, again, she is a teenager... and I doubt there are many teenagers (or those of us who were once teenagers ;) that never made a mistake. She tried to move on, but she really wasn't ready to. But I don't think she "used" Harry. I think she tried to make the relationship work, but as there were faults on both sides (Harry never tried to get to know her either), it was doomed to fail. For every step she took forward, she took two steps back.
Yes, I know - if you are a Cho-hater, you don't agree with me. Let us agree to disagree. I merely want to say that I don't "dislike" all Cho-haters.
The ones I do "dislike" are the ones that say comments such as:
She is a whore. She stole Harry's mouth-virginity. blah blah blah.
Those are the Cho-haters I dislike. For one thing, we've only seen her date three guys (Cedric, Harry, Michael) and she only mentioned Roger asked her out (but they never went). Uh-- didn't Ginny date as many guys too (or maybe more)? I don't see (at least, I haven't seen) anyone call Ginny a "whore". And what about Ron? He only dated Lavendar just because he wanted someone to snog, and he was a coward (a bit contradictory since he is a Gryffindor) when he wanted to break up with her. But I digress. The Cho-haters specifically hate that she jumped from Harry to Michael. Well, time had "passed" since their argument (to which I say - Cho was showing loyalty to Marietta, just as Harry would show loyalty to Hermione and Ron - so why couldn't Harry see that? also, Neville in SS tried to stop the trio (and Hermione stupified him? when he stood in their way) so I see parallels there too. Sorry, I digressed again.) and who knows what happened between Cho and Michael. Maybe Michael showed Cho a little more compassion and consideration than Harry ever did.
Ok, I think I'm done rambling...
I just wanted to say the Cho-haters I dislike are those that act that way, and say those things. If you "hate" her because she cried or was not a good match for Harry, then I don't hate you.
The same goes for Katie-haters. If you think she's a terrible actress (which I don't agree, but that is your opinion), then I respect that. But I do "dislike" Katie-haters who confuse Katie with Cho, and scream that Katie will get to kiss Daniel when they can't.