There's a lot of trouble 6 year olds can get into in most homes, guns or not. There's a lot of bad stuff that can go happen in the home of someone you barely know.

I get the concern, but the original poster's concern seems on a level of finding out the other Dad was an ex convict or a Republican or something(gotta get my shots in where I see 'em).

It sounds like the real mistake was allowing his child to be in a strangers home alone in the first place. A bit weird... but what do I know... I'm way WAY too irresponsible to have kids. Luckily, for society, I am responsible enough not to have them.