I need your opinions on backround checks?

I've found that once you sign, they can look into anything they want. I gave this place permission for a background check (for criminal violations) and the next thing I know they'd pulled a credit report. I knew I had bad credit and never would have submitted to it if that was the case and yet I knew I had no criminal background. So they didn't hire me. How wrong is that? Logic appears to have no basis for any of this... not having a lawyer with me, I dunno how it all would have panned out if I'd tried to contest it.