In my honest opinion, it's easy to like Federer if you are a Nadal fan. Nadal basically owns Federer and he's no threat to him by any means. Even I sometimes root for Federer against Nadal because of it and sometimes I think it isn't even fair. If the rivalry was more even then perhaps it wouldn't have been so easy.
I am actually more indifferent to Federer these days than ever before. I used to not like him as much because I found him a bit arrogant, but my feelings are more neutral these days. Sometimes I even feel sorry for him because he's declining and we'll probably never see him again, so that's always sad to see when a great player goes away. I can relate because Pete's retirement was one of the hardest things Sampras fans had to go through.