Baby Name Poll

Hello, I was on this site last month to ask if people thought it was weird that I was going to name my son Matthew when my sister was engaged to a Matthew. I went ahead and did it because I love the name and because there are tons of people in my family with the same or similar names. A friend of mine, as well as someone on this board, suggested it wasn’t a good idea or that I should ask first because my sister might want a Matthew Jr. Others told me if I had a son first, I should do it because names are first come, first serve and you can’t dibs a name (which I think someone heard on this site) I still intended to use the name, but I asked my sister hypothetically what she’d think of a situation like that, just to see. She said the same thing, that you can’t dibs a name and you can name your kid what you want and don’t have to ask permission. So it’s all good. But my some friend’s are still being negative about it. They’re calling my selfish and said that they’ll be soooo mad at me if my sister ever wanted the name Matthew for a kid (which she doesn’t). And when I tell them my sister thinks the idea of naming a child after herself or her husband is conceited, the get mad at my as if I’m the one that feels that way. What should I tell them.