I don't understand why this father is pissed off at his ex for getting his deaf son a cochlear implant.
The only thing I can think of, that may be pissing him off, is that since he, the father, is deaf, he feels that his son would be fine being deaf too for the rest of his life. But now that his ex has given his son the gift of hearing, he seems pissed that his son is no longer deaf like him.
This is the only conclusion I can come up with as to why this father feels so angry towards his ex for doing something so wonderful for his son. If I were this father I'd be overjoyed that my son could now hear and have the opportunity for a better and easier life than myself. But apparently this guy is too self absorbed and angry at his ex to be able to appreciate the wonderful opportunity she has given their son.