Tallbloke, if you found yourself in trouble after an incident and went to your union for help, would you not expect to get it in accordance with the relevant laws, rules, agreements and your legitimate entitlements as a member?
How would you feel if you then heard that "the word is out that you were more wrong than right in what you did" and that the union had decided that, since it would be unpopular with many union members, they were going to decline to fight your case? I suspect you would be rather displeased. You might argue that your entitlement to support should not be subject to a popularity contest! You might even argue that this is just the type of difficult situation you had in mind when you joined.
*******
To my mind Virga67's comments from outside the U.K. really put this matter in a proper perspective. He has the advantage of a bit of distance and experience of the long-standing arrangements in KLM.
Flying is now no different from a host of other occupations, in which more and more people want flexibility in how they arrange their work. Is there anything wrong with seeking appropriate arrangements for everybody in accordance with changes in the law?