Stop telling me I'll be a good father. Its disrespectful
Seriously. It shows that you don't know me at all. I get that its meant as a compliment; the statement is often followed by an appreciation of my character, but it shows a lack of respect for me as a person.
What makes you think that I, a person that does not want kids, would be the same person if I was put into that situation? I am able to be that kind of person you describe because I get my alone time. I am independent in my way of life, I need to be left alone from time to time to recharge and reflect. I need to be able to go days without talking to people if I want to. If I were to have a kid I would lose that ability and I would feel robbed because of it.
Whats even more disrespectful is the lack of active listening you've done in previous conversations. You should know that I don't want that house with the picket fence. If you've done any listening you would know that I would much rather spend parts of my life in a sailboat or on the road doing odd jobs for money. That is not a good life for a kid, and what makes you think that I'd be the same person if I would have to give up those dreams? It shows a lack of comprehension and emotional understanding when you don't consider what having kids would do to my sense of freedom.
You have this ideal of me that you want me to become some day and you think a kid will magically flip the switch somehow. You want me to become someone I'm not, and thats why its disrespectful. It shows that you want me to live the life you wanted, and you're invalidating my wants and needs to confirm your own. You need others to make the same choice as you to assure yourself that you made the right call when you decided to have kids.
Sorry (not really) but I don't want kids, its not who I am and I wont be the person you know if I had one. The next time someone says I'll be a good parent, I'll respond with “Thanks. You'll be a horrible one.”