Big Mistakes

I was a bit disappointed with how my father is acting today.  One of my niece left a message in facebook showing no respect on my dad.  My dad might did something that she was not happy but it was enough that she will just call my dad by his name.  So to correct her;   I posted a comment no matter what happen he is still her grandfather her grandmother brother so please still show a little bit of respect.  i thought everything is find but my sister comment back and now my dad.  My dad will tell the whole world through facebook what kind of girl she is.  As the older person he should just ignore but instead try to make everything go bigger.  Sometimes I just wish my dad to grow up a little. 
Now I am thinking was it a big mistakes of me leaving a comment to this girl?