Have you ever heard or noticed someone getting upset about another person picking on their family, but then turn around and pick on their family themselves? That is what's at work here.
Posideon has grounds for taking Odysseus to court in that:
1. Odysseus committed assault on his son. Polyphemus had his eye burned and singed. There were eye witnesses and accomplices. A plan was thoroughly discussed and enacted.
2. Odysseus committed fraud on his son. Odysseus claimed that his name was Nobhdy. Only on a binding document would this ever matter, so this one is shaky, but worth a try.
3. Odysseus harassed his son. The name Odysseus declared prevented Polyphemus from receiving any help from neighboring Cyclopes.
4. Odysseus committed grand theft ram. Odysseus loaded several sheep, goats, ewes and rams onto his boat upon departure.