> Why isn't it valid to say you don't like unions and so don't want anything to do with them?
Because you can't possibly have personally experienced every union, and the media isn't good at covering unions generally, so whatever bias you're (or anyone else making this statement is) presenting here feels unearned.
This is similar to the bias of racism or homophobia, right? Like, "I saw a Black person steal something, so now I think that all Black people are untrustworthy." Or, "I saw a gay man hit on a straight guy and now I think all gay men are sex pests." These are declarative statements about all people in those groups based on a small amount of information and on societal bias.
And these biases rarely go the other way – do you also end up saying, "I don't like corporations and don't want anything to do with them?" Corporations are, by far, have a vastly worse record on theft, corruption, anti-environmental practices, etc.
