I hate these banners and silly slogans.
Someone asked me to display an “I’m against child cruelty” sticker in my window. She was a bit put out when I donated, but declined to use the sticker. Surely it’s a given that one is against child cruelty ?! 
I agree that the “be kind” thing is often shorthand for “shut up - I don’t approve of this subject”. I’ve seen it on MN, used in rather a menacing way...