I agree that it's not within the remit of RMT to cover other sectors, however there is a harsh reality here. We will always need nurses, police, teachers, refuse collectors etc, but the railways are more expendable. Everyone needs nurses etc, even though many might be fortunate enough not to need them yet, all of us have needed teachers in the past and many still do for their children and grandchildren, and so on, but the simple reality is that around 40% of all people in the UK haven't used trains for many years, and something more like 90% could do without them if they had to. Trains are a "nice to have" option, but a far, far greater proportion of the population rely on cars and can, if necessary, manage without trains. What this strike is doing is training people how to live without the railways.
I've been a lifelong rail user with a lifelong interest in rail operations, but most people I talk to can take or leave them. The RMT might be stronger than Unite etc, but it would be a huge own goal if they ended up with much less to fight for if the industry shrank due to disillusionment about their reliability. And quite possibly the dissuading effect of fare increases which will be needed to cover the wage and other demands. I don't approve of unreasonable management tactics any more than anyone else, but I do think that strikers need to be careful if their primary motive is purely financial.