For me, this is a purely emotional response. If in your shoes, I would feel like he was pushing me to choose between my children and him. For me, there would be no contest. My child would win out every single time.
I could understand his reaction if your kids were not contributing, not going to school or working and just sitting around. But I guess I see this world as a tough one, and the fact that they are both going to school and contributing tells me they are well raised, decent young men. I would tell him to to either like it or leave. That's just me though and again, a purely emotional reaction.
I agree with Annie, and I think his attitude will be as begrudging toward them 10 years down the road and they want to bring wives and kids to your home for a visit. I really wouldn't choose to be with a man who is "done" with his kids when one is still a teenager.
Well, he sure sounds like Mister Fun. Didn't you take a clue when you were dating, that he had teenage boys himself who like him so little as a father that they won't speak to him? I don't understand why his conditional attitude about your kids would come as any surprise.
Though stepparents can be more grudging towards their stepkids than their kids, Jason doesn't even sound like he is pleasant or reasonable with his own. (He's "done raising kids" when he has a 17-year-old boy? Doesn't he have any clue how important a father is to a 17-year-old?) This makes me think you can't change him with something you say.
What you can do? It sounds like your choices are to stay (to the slight detriment of your kids who are now nominally adults and should be able to handle it) or to say, "Jason, you have said something needs to change, here is what is going to change, me. I am leaving. That should solve your problem."
I don't necessarily recommend the second choice, your kids are not babies and are on their way out the door. If you like the guy and otherwise like being married to him, stay. But don't expect his attitude to change.