Insurance seems to by-pass a lot of problems in this case, especially HIS insurance. Lend any one (that you can afford and feel comfortable to miss for some time). He's a friend so he should be able to understand the lens means something to you and return it within a decent period, undamaged. If, however, he damages/looses it, he should tell you so straight away and take steps to replace it right there and then. IMO that's what friends do among each other.
BTW, if you think you can "buy" his love and interest for you by lending him the lens, you're on the wrong track. Love can never be bought. I strongly advice you to find different ways to get his attention and love. A shooting outing might do, which will give him to opportunity to test run some of your lenses as well.