In general, WWE is doing ok with the Bo Dallas character. Most of that has to do with Bo being so awesome at playing such a unique heel, but the segments booked with Daniel Bryan and the post match motivational speeches are just great.
That being said, if they really want people to hate the character, it can't be Bo telling people how motivational he is, or even JBL. THE COMPANY has to be the one doing it. The Bo character takes most of what adult fans hate about Cena and turns the dial to 10.
What helps garner Cena a good hunk of his adult heat? Michael Cole talking about how inspirational he is when he rises above. Do that for Bo. Have Michael Cole go on and on every week about how great and positive Bo is. Have King do it too. It can't just be JBL liking him because he's a heel and Cole disliking him because he's a face (face/heel announcers annoy me anyway, but that's a subject for another time). If the entire broadcast team sings his praises, especially if they're small, he will be the most despised man in the company. Instead of having the machine get behind making people hate him, they should actively force people to like him. That way, they can generate some organic heat. Nuclear heat. "Die Rocky, die" heat. It would be the perfect reality era heel. They could even book him like a face, but he would be the top villain in the company.