Why can't someone prefer it if someone they look up to doesn't smoke? Assuming that Keira is a role model to some people, self-electedly so or not, people will hope she does things that match with their idea of "a good person," not to mention a healthy one.
Lord knows I notice when the 27 guys, 36 women and 116 teenagers smoke. BECAUSE I CAN'T BREATHE.
Just because you're allowed to do it doesn't mean other people aren't allowed to dislike it.
And just because you don't give a shit doesn't mean Keira's fans aren't allowed to. You know, the target audience of these forums?