Because they don't like to hear it like it is. Paul was hand picked by Jesus to go to the Gentiles. Jesus knew Paul inside and out and knew he could get the job done. Paul could be caustic but his words were those that Jesus wanted said. As a result, many people don't like him. They fear the truth and Paul piled the truth on them.

“In a time of deceit telling the truth is a revolutionary act.”
― George Orwell

It's not over when you lose. It's over when you quit.