Sounds to me like you may be a little frustrated at one of his machines and might be taking that frustration out on Bob. The man doesn't know you from Adam, you buy one of his machines (at a lower price from someone else) because YOU have researched it and want it. You tried adjusting a part in a way that the part was NOT intended to be adjusted and you BROKE it. Most people would charge you FULL PRICE to replace a part that YOU broke, however, Bob is merely explaining his position regarding the part. On top of that, he is going to REPLACE the part YOU broke for FREE!
He's willing to GIVE you a part to fix a 5+ year old machine that YOU bought from SOMEONE ELSE that YOU BROKE, and you think HE is being unreasonable? If I were you, I'd be adding Bob Tippman to your Christmas Card list this year AND tell everyone you know how fairly and professionally Bob Tippman treated you when you had a MAJOR problem!!