The risk of drinking alchohol with taking insulin is that anybody can mistake a hypo for drunkedness and vice versa...
Even one glass smelt on breath can be enough for police or ambulance people to assume that you are drunk not hypo......they should test bloods immediately, no matter what their opinions are...
An explanation liking it to not drinking and driving may help son to realise that some people do not drink to go out and enjoy themselves, (or even staying in..)...drinking in excess is really best avoided when a T1, although it seems that alchohol is more prevalent today than when I was a young adult when alchohol was only a babycham at xmas.
I would really do utmost to find out if blood test was done on arrival at police station...