You Bleed For Me, I'll Bleed For You

I killed a cockroach today. I'm not a murderer. Or am I? Why is it okay to kill a bug? Yeah, we don't eat bugs, but its still one of G-d's creatures. I don't eat pig, but that doesn't mean that if I saw a pig on the street I'd swat it over the head with a fly (er... pig) swatter to kill it. And I wouldn't step on it and squish it to death. So why is it okay to do these things to bugs?

My head hurts...