Would you keep your child's car seat if 3 firemen and 2 E.M.S. people told you it was okay?

I have a very expensive Britax car seat that my son loves. We were in a rear end crash and I assumed it would not be safe to use. Some on lookers, stopped to help, and a lady came over with her son's car seat (he wasn't with her) and offered it to me. One of the nicest things anyone has done for me that I can remember. The E.M.S. stepped in and told her to go back to her car, and my car seat was fine. I told him I was taking hers and I did, but he assured me that his car seat was fine, and then to, as he said "appease me" he asked 4 other officials on the scene, all who looked at it and told me it was fine. We were still at a light, and the guy who hit us was going 30 mph. so not so fast, but enough to move my son's car seat a little, so I know it was impacted... So what are the real rules on that? I mean I love that car seat and it sat me back a pretty penny, but why would they tell me it is okay, if it is not? Is it really garbage, or is it okay as they told me?