Here is the link to the Teamsters official announcement
The Teamster's spokesperson provides some reasoning as to why they made the call, though its a PR event.
Here is the Biden's campaign page regarding unionized labor.
One could always read and consider these documents, as opposed to expressing knee-jerk anger at the discovery the world doesn't align perfectly to one's own world-view. But I expect such items might be instantly regarded as lies to be discounted based on their source. Meanwhile, a cursory and basic Google search turns up quite a few articles generally advising President Trump is adverse to union interests. I would not claim these are unbiased sources- but not many "Trump is pro union" articles pop up.
I'm a Pro-Union Teamster. A liberal. And I disapprove of Trump.
I exist. And there seem to be a couple others in this thread that are similar. So are the Teamsters really out of touch with their membership, since we are members?
This Browncafe site seems to have a vocal conservative membership. There is nothing wrong with that. But beware an echo chamber of your own creation. There is one person here saying they outright block anyone who supports Biden... a person actively and intentionally making their comfortable-ideas space smaller and 'echo-y-er'. They don't get more snowflake than that.
Don't be like that guy.