The bottom line about this never-ending argument is that nothing changes. I have seen the odd person on threads like this say "you know what, I'd never registered how important these facilities are. I've popped in before, but I won't do it again" but those who take the time to argue their points are the ones with the most entrenched views, and they're not going to back down.
The people who are arguing that they have a right to use these facilities clearly aren't going to stop doing it. And the people they are arguing with have no power to either force them to stop, or grant them permission to do so. So all these people are arguing for is for everyone else to stop thinking badly of them. They want to do what they want, and not be confronted with the disapproval of others. I can only assume that the continued passionate defence of what they are doing is because deep down they know it's wrong, and they don't like feeling bad about it and want someone else to tell them it's okay.
The people who feel that these facilities should be kept available for those with a genuine medical need for them are not suddenly going to decide that it's not so important. They're not going to give that permission or tell other people that it's okay. They're going to carry on thinking badly of those who use these facilities without a legitimate need to do so.
So if you choose to carry on using these facilities, even after all the reasons not to have been laid out for you by those in the best position to assess their usefulness, then that's what you are going to do, and nothing anyone else can say is going to change that. But don't expect people not to tut and glare and think you are entitled and selfish. Because that's what they're going to do and nothing you can say is going to change that.
I have two small children. I do not use disabled toilets because I am an able-bodied, competent human being who is capable of coming up with a solution to my needs that does not impact on anyone else.
Make your choices, by all means, but don't then have a hissy fit because it's not all smiles and sunshine and people gazing at you and your adorable children with an expression of gentle benevolence.