Welll, I don't truly hate Amon. Ok, I (used to) hate Amon. But not Noatok. (Water tribe names are hard to spell, so I'm wondering if I got that right?)
Anyway, yes, having romantic feelings for another person while you're dating someone else is cheating.
I only hate Cheating Mako. I don't hate all of Mako.
I didn't count the end episode for his cheating. Because it wasn't cheating. He'd broken up with Asami already, and really, before that. (Unofficially when Asami found out about Korra and Mako's kiss. That's my two cents on it, anyway.)
So, no. To re-cap, I don't hate Noatok. I hate Amon. I don't hate Mako. I hate his cheating self.
Also, this may just be me, but I don't find Amon likeable. No offense. Noatok, however, was. Amon was presented well, even the youngest kid watching could tell he was a villian. But with Noatok, you really did feel bad.