By federal law, if a company has a union, the union must represent ALL non-management workers, even those who do not pay dues.
This is obviously fucked up. But this has been union law at the NLRB for a long time.
The fair response: a union should only legally be responsible for representing its members. But these sorts of terrible union laws are the consequence of attempting to destroy them since their creation.
And for those of you who think unions are terrible (capitalists and ilk), what we had before was 'firebomb the business or the bosses house', and basically waging war between capitalists and labor. Unions and legal representation WAS the compromise.
Labor history has always been a bloody and murderous affair. Go look up the history of the pinkertons.