AITA for shunning a creepy family member?

It’s a long story and I sincerely apologize.

Basically, I have this cousin who we will call John. John is in his forties and married with three grown children who all still live at home. John is also a... shall we say, “looker”. I am 23 and married with no children.

My 14-year-old niece has come to me once saying that John gives her a weird vibe. He hasn’t done anything, but she’s caught him looking at me and some of our other family members. I asked her if she had caught him looking at her. She said no.

So anyways, my whole family went to one of the local lakes for Independence Day in the United States. I caught him looking at me in very creepy manners more than once. Now, I am working on my courage. If I had caught him staring at my niece or other cousins, shit would have hit the fan. I do, however, have a really hard time standing up for myself. So I said nothing.

Until I was visiting my mom’s house tonight who is planning my state’s holiday, which is the 24th of this month. She said she was considering inviting John and his family.

I informed her of what had been happening at the lake. She had been aware of what my niece said prior to the lake.

Her response was, “well, I don’t think he’s a toucher, and you can’t stop men from staring.”

To which I said, “imagine for one moment that you’re wrong and (my niece) or someone else was hurt. How would that play out? Additionally, men should not being looking at girls who are A. minors or B. their family.”

Now I’m not being spoken to, or invited to the festivities of the 24th because ‘that was just too far.’

So, AITA? I genuinely do not think I am the asshole, and if I am, I am open to constructive criticism.