I really don't understand why people seem to forever condemn Hook for his past. He was a good, honorable man before bad things happened to him and he basically decided to give up being good. Was that the right thing to do? No, but he didn't really have anyone to show him a different way. Did he do horrible things during his dark days? Yes. BUT he realized that being bad was getting him nowhere and started to turn back into the good, honorable man he once was. IMO, THAT is what matters.

He also doesn't JUST hang around Emma. In 3B alone, he helped David and Robin look for Little John and even went to the hospital with them. He was with Belle on 2 occasions during Quite Minds and visited Neal at the hospital. He was with Smee at the docks when Emma came to him to watch Henry. He was alone with Henry at least 3 times. Hell, most of Jolly Roger was with him and people who were not Emma. As others have said, OF COURSE he is going to spend the most time with her as she is his LI. Same reason David has always shared most of his screen time with MM.