I would like to add that your boyfriend is probably young?
People learn to deal with situations differently as they get older and are more mature.
It is a plus that he would drive a drunk friend home rather than risk attending that friend's funeral.
It is a minus (and probably just an immature one) that he caved under his drunk friend's pressure.
The situation that YOU will need to deal with here is whether you hang on to this one instance or let it go.
If it is a real problem and NOT immaturity on his part you'll find out sooner or later and can decide from there what to do with the relationship.
But, the guy caved, made a poor decision. If you make a mistake in how you deal with something down the road, how do you want HIM to deal with YOU?!