What to do when an ex has your child calling a new bf daddy?

I know there is basically no legal recourse, at least in Texas. My son is 2, we have joint custody, he's w me 65% of the time, and she's recently introduced a new bf in his life. She's gone so far as to make a video of them trying to get my son to call him daddy and post it on Facebook. Obviously this is a malicious attempt to get at me but I refuse to engage in Facebook war/drama. But most importantly I don't see how this isn't borderline emotional trauma and manipulation of my 2 year old son, especially when his father is primarily raising him. Advice on how to deal with this?