Maybe this is how Snape really is. On the outside he's mean, cold and "I don't care about Potter" but on the inside he actually loves the boy. It doesn't really make sense to me that he'd hate rather than love Harry because he's Lilly's son and he loved Lilly. Harry's James' son and Snape hates James but he's also Lilly's son as well, meaning that he'd have a love/hate relationship with Harry. Truth is, Snape just wasn't a nice guy (I think he was actually worse to Neville than Harry in many ways and Neville was more sensitive than Harry.) I also wonder if Snape even knew how to show kindness, very few people showed him genuine kindness during his lifetime (which makes me very sad, no one should have to live like that.) Even if he loved Harry, he probably wouldn't know how to show it (he didn't even know how to show Lilly that he loved her and insulted her straight to her face.)