To be honest, at some point you just have to do the switch if you care enough about your privacy by deleting the messengers you don't want to use.

I was there too. No amount of convincing is going to change their mind. They have to make the decision which messenger to use themselves just like you do.

You may look like an asshole by moving away from the "common ground" but imo that's worth it. They don't realize that they are the ones being disrespectful by valuing being lazy over your feelings of privacy.