A: Live your life as though they don't exist! They want a reaction from you, don't give them what they want and live you life without them existing to you!
I ignored neighbors like that, eventually they realized they were fighting with themselves. There are three P words you chant when you see them know they are pathetic, pity them then pray for them!
Remember: PATHETIC, PITY then PRAY.
If you really want to piss them off, simply say, "have a nice day."
Mean people have a hard time responding to kindness!!!