I don’t see any reason that they preclude it. A person who makes jokes instead of taking action wasn’t really going to take action anyway.
And perhaps jokes/insults themselves could constitute action. Imagine the psychological effect on Trump of a popularly shared humorous re-enactment of his alleged pee-pee party. (To be truly popular, it would probably have to avoid any genuine depiction of water-sports, of course.)
Depends on the phone, but it’s usually not difficult. There are lots of options for backups, and lots of options for encrypting the backed-up data. The EFF link in my comment has a lot of good info on the topic (the part on mobiles is lower down on the page).
One thing I would suggest is to restore an innocuous but polluted “border-friendly” backup after wiping the phone of the everyday stuff. If things continue as they are for a few years, eventually having a blank phone will cause more problems than it solves if it’s searched. I don’t have Facebook or Twitter, but I’ve been thinking of setting up a dummy Facebook account for this purpose.