I agree with your friend, you do sound like a patronising elitist. I play football and can run 5 miles in 31 min, trying to get under 30 in a race this year.
And if he can do a 5 miles in 31 minutes without much training I can see him getting very close to a 5min 1 mile. Hope he proves you wrong.
I wouldn't join a Leinster Senior League soccer team in the morning and expect to walk straight into their team on the basis that I play five-a-side twice a week.
By the way, if you're hoping for sub-30 for five miles and are only running part-time then I'd suggest packing in the football and joining an athletics club! That's very good going.