Mike

I want to point out that your friend wants to put the blame on you. I suspect that he is being pressured by his new girlfriend. Regardless, he is not taking any responsibility.

You can sit down with him and say “Bob, I am sorry that you are upset that Jill is coming to the wedding. You are my best friend and I hope you see me as yours as well. This is the most important day of my life and I hope as my best friend you can support me in this stressful time. Please reconsider and set aside your differences for this one day of celebration and happiness for your buddy. Your friendship means the world to me and I hope you can focus on my wedding rather than your ex.

Can you do that for me?”