Your friend, best case scenario, is "cruisin for a bruisin". I don't know his rationale but, if he is counting on academy DT training exclusively to prepare himself for a confrontation, he is in for a rude awakening. Many BGs have been fighting all their lives; with their families, with their neighborhood, with school, with rival gang members, etc. They may or may not have much skill, but they know what it's like to be beaten, cut, or shot. Over the last month or two, I've met a couple of inmates who are "cage fighters" (UFC minor leagues).
A week or two of basic force/personal weapons in the academy is not going to cut it. The DI's realize that, due to time constraints, recruits are not going to given as much training as they need and they strongly recommend that everyone, if they haven't already, join a gym/school and consistently train after graduation and throughout their careers.
In law enforcement, my opinion is that there is no excuse for not training. Your life or your partner's life may depend on it. I have a little experience and, when I try to share it with my partners, most of them don't make the effort to learn. Some of the reasons are understandable, i.e. family, work, other personal issues etal. But "I have a gun, I'll just shoot them" or "my partners will back me up" is not.
From my experience, the guys on my department who do train, can kick some butt. For the most part, however, they are in the minority. When I've helped out our force training unit for patrol school (and at the academy level), I've noticed that most trainees are not skilled enough or not mentally prepared enough for a physical confrontation.
I don't have a "tougher than you" attitude because I've been choked out, arm barred, had my bell rung, etc too many times by too many different people. Sometimes, and I hope this is the case with your friend, people don't train because they have no idea what's out there or how unprepared they really are.
I really like Crayola's idea. Find some unassuming-looking guy or gal with experience/ability and have that person Kick Your Friend's Butt in a "clean/friendly" UFC- type fight (with no weapons and no dirty techniques). Then point out how much Worse it could have been.
Humility-wise and however skilled/experienced you are, you should still realize that, On any given day, there's going to be someone who can kick your butt. Officer survival-wise, the way you think should be, Ok, but it ain't going to be TODAY, and it ain't going to be HIM.
Try to have him train with some good people, "just to see what it's like". When I work out with beginners, I see how far I've come. When I work out with my partners and instructors, I see how far I still need to go.