Here's how I see that whole messy scenario: Taka was emulating Mondo at that point, and Mondo had a very strict code of honor when it came to hitting girls, that being don't fuckin' do it. Given how much Taka idolized Mondo, I find it highly unlikely that Taka would've insulted Mondo's memory by raping a woman, no matter how crazy he was. Hifumi, unfortunately for him, was too much of a gullible idiot to think critically about the situation, and then there'd also be the issue of him being executed with or without having to endure another class trial, which nobody except for Byakuya and arguably Kyoko (because she likes solving mysteries) actually enjoys. So I do think it's understandable why he so readily believed Celeste, but he really could have handled that situation better.
That's my take anyway, I haven't actually played THH in a while so it's not exactly fresh in my mind.
Yeah, I think you're pretty spot on. Like, morally I think he was justified in doing what he did (because fuck rapists), but yeah, he's a complete idiot.