The suitors are in the process of eating poor Penelope and Telemachos out of house and home. They transgress all traditional ideas of honor by proposing marriage to a woman still waiting and grieving for her husband. They don't show any respect to the man of the house, Telemachos. Oh, and they also beat up beggars.
Poseidon is a more distant villain than the suitors, working his magic from afar and never confronting Odysseus face-to-face for any sort of showdown. Of course, this makes it difficult for Odysseus to best or beat Poseidon in any sort of traditional way; instead, he has to make peace with his enemy after suffering the hardship of his punishment.