Because they were shit on in the past. On the one hand, they have a point about the record profits stuff.
But on the other hand, they are timing this for the elections, and the leader bragging on social media that he could cripple the United States (and will) is not going over very well with people who are not union workers. I know he thinks one of the Presidential candidates is his friend for inviting him to his place in Florida, but when million-dollar and billion-dollar companies and their customers get pissed, they are going to want somebody to come down hard on that guy and the other union workers. Do they really think that the Texas Governor, who has been bragging non-stop about the Texas economy in recent weeks, is going to be happy to have cargo ships clogging up the Houston Ship Channel? Because a lot of companies are going to be leaning on every politician to shut this down.
That guy really fucked up with his "we will cripple the US" nonsense. That was the epitome of arrogance.
If he had simply stated the case about the record profits, the COVID stuff, etc., that would be reasonable with a lot of people (although many are going to be wondering why those guys get six figures for moving stuff on and off ships), but the cripple comment was a true fuckup.