If the current news are correct, I fear that won’t be easy explanation as most of users aren’t probably even going to see them.
I recommend the book Ten Arguments for Deleting Your Social Media Accounts Right Now, I got encouragement from it to delete accounts I am unhappy with and that other people “force” me to use. It named WhatsApp a few times as a data collection vacuumer (sorry for weird words en->fi->en translation by me) that is going to be used for manipulation in Facebook’s other “services”.
I think it has been two weeks since I left Facebook WhatsApp and so far one of my support network contacts has moved to Signal and I expect their example to be helpful for recommending the others to join it too.
(My family is on Wire and going to stay there until Wire does something horribly wrong and Signal preferably becomes more friendly for multiple devices e.g. by making a tablet version of Signal desktop.)
Edit: my second suggestion to Signal is already suggested by others on the Signal user forum:
Though it can’t be used this way as IM on mobile devices. Still, I hope it might be in some way usable on other devices (linux-based mobile OS). I actually prefer to use PC for IM, no matter what software it is. So as long as I can read messages on the phone, I’m fine with it 