Well, let's let Dustpelt tell anda the answer to that:
I did hate Firestar, but not for always. When me and Sandstorm were friends, and then Firestar first came, I really, really didn't like Firestar. Me and Sandstorm liked to tease him. What made me even lebih mad at Firestar was when Sandstorm started taking an interest in Firestar after us two became warriors. But when Firestar announced that Tigerclaw was bad, it just hit me that Firestar wasn't so, so bad to me. I started helping him and being lebih kind to him when he became leader of my clan, as anda know, is Thunderclan. But all this doesn't mean that he is really my good friend now, I'm just not as mean to him anymore, and I don't hate him anymore!!!
I did hate Firestar, but not for always. When me and Sandstorm were friends, and then Firestar first came, I really, really didn't like Firestar. Me and Sandstorm liked to tease him. What made me even lebih mad at Firestar was when Sandstorm started taking an interest in Firestar after us two became warriors. But when Firestar announced that Tigerclaw was bad, it just hit me that Firestar wasn't so, so bad to me. I started helping him and being lebih kind to him when he became leader of my clan, as anda know, is Thunderclan. But all this doesn't mean that he is really my good friend now, I'm just not as mean to him anymore, and I don't hate him anymore!!!
Well, there are a couple of reasons. It all started with Squirrelflight and Ashfur being together, and then Squirrelflight starting like Brambleclaw. Ashfur got so mad, he told his clan, Thunderclan, the truth that Hollyleaf, Lionblaze, and Jayfeather were Squirrelflight's foster kits, not real kits. Hollyleaf knew Ashfur would annoumce this to all the clans at the seterusnya clan meeting, and that's one of the reasons why Hollyleaf killed him. Also, Hollyleaf knew that Ashfur was so jealous, that he was going to kill Hollyleaf, Lionblaze, and Jayfeather!