Holden actually likes a lot of things; he just doesn't know to articulate them. He knows, for example, that he likes his little sister Phoebe and his dead brother Allie. The obvious reason he likes these two is that they are young and innocent. Phoebe is still very much a child, even though she sometimes seems very grown up for her age, and Allie is forever young, because he died before he could be corrupted by society. But it's also clear that Holden likes the rest of his family too, so much so that he doesn't want to see bad things happen to them.
For example, when Holden's mom sent him skates for Christmas, he didn't return them or tell her they were the wrong kind of skates, because he felt bad. He knew that the lack of communication between him and his parents was the cause of the problem. He doesn't want to disappoint his parents. He doesn't want to tell them his got kicked out of school (again), because he knows it will hurt them so much. The same rings true of his older brother, DB. Holden talks about what a wonderful writer his brother is, but he laments the fact that his brother is prostituting his talent in Hollywood writing for movies. This shouldn't be read as an attack on DB, but rather as a reflection of Holden's idealism. Holden is so often disappointed by people because he sees the potential of humankind, and then he sees people not live up to their potential.
He likes Mr Spencer, or he never would have shown the respect to go to his home before he left Pencey. He likes Mr Antolini or he wouldn't have felt so bad for running out of his apartment. He likes the nuns or he wouldn't have given them so much money for their collection. He likes Mrs. Morrow or he wouldn't have made up such an elaborate lie about her lousy son. He very much likes Jane, which is why he refuses to go talk to her - his deepest fear is that society has corrupted her too.
Holden is a good guy who sees the world as it COULD be, so it just seems as though he doesn't like people. A kid who doesn't like people certainly wouldn't rub profanity off the walls in public places just so little kids didn't have to see it; he'd leave it there.