Unfortunately, that's an overreaching statement. I personally know a few people who have accepted pay cuts to leverage the type of job security afforded by certain unions.
>> How many unions in the private market can really claim you wont get fired.
Certainly none, but does it really matter? There's exists a threshold where the difference between won't get fired and very difficult to get fired are pragmatically indistinguishable.
And yes it matters as the parent wanted to dismiss unions based on these false claims.
Unions are neither good nor bad. Some of them have too much power, others have too little. Some should have a union (like uber drivers) etc.
My own father tried to start a kind of union for a group of self-employed drivers working for one company. The result was that the company he worked for simply stopped his contract and scared everyone else off from backing him and a few others up.
I have seen unions be both really bad, really good, unnecessary and not existing where they should.
They are no different than consumer interest groups and other collections of people trying to reach some sort of balance.
In many industries today they aren't needed but in some they still are.