He also was saying Kirk was too hateful

This information comes from a misquotation. One example of the story with this information has the full context:

Cox said that a family member of Robinson had told investigators that at a recent family dinner, Robinson had mentioned Kirk’s upcoming event at Utah Valley University, and “they talked about why they didn’t like him and the viewpoints that he had,” Cox said. “The family member also stated Kirk was full of hate and spreading hate.”

Note that the family member is the one who said “Kirk was full of hate and spreading hate.” But it has been repeatedly misattributed.