SUPers, Longboarders, short boarders, groms, boogies boarders - don't we all have compliants about each of the groups. Longboarders complain about SUPs, short boarders complain about long boards, etc, etc. We have all been snaked and all have been dropped in on and we have all had to share waves - even if not technically dropped in on. I'm sure we have all done it to others too - whether intentional or not. End of the day, it all comes down to etiquette.
Some SUPers at my break will ride the bump and leave the break to the surfers, tell someone to come in with them and sometimes signal when a set it coming in. I've waived guys into waves with me, tell someone else to keep paddling when I don't think I'm going to catch it so someone grabs the wave. I won't snake but have dropped in - either not seeing the guy other guy, thinking he was going the other way or because I was far enough ahead to not get in his way. I will pull out the wave if I think I messed up and will always apologize.
Surfing is soulful - I don't want to go surf with bad vibes in the water - I surf to feel the stoke. And a little thoughtfulness goes a long way to keep the vibe good.