Not to single out the particular comment, but to illustrate a more general concept:

It is an obvious and well-known fact that if you are in danger of getting fired for not being able or willing to do your job, you just file a union grievance and you have instant job security.

This is true only if the contract includes a "seniority rule." The contract is negotiated between the company and the union, and nothing can be included in the contract unless both sides agree to have it in the contract.

When, as is common, the company complains that "union wages are too high" it's because that's what the company agreed to pay, but now they've changed their mind.

And although not emphasised, I did intend to suggest that the majority of workers in the US are not covered by union contracts. There are any number of laws and regulations that provide, in varying degrees, some restrictions on working conditions and employee/employer performance expectations, but even the "tightest" of union contracts is unlikely to even remotely approach the "sea squirt tenure" notion applicable to a separate select few in some specific "industries."

John