why honesty is not the best policy

Don't get me wrong, I want you to tell me the truth. There is the horrible trend out now among children. They feel the overwhelming need to have word vomit all over me and my children and other children.... and when I look at the parents after such rancid comments, usually i'm getting the excuse that "atleast they're being honest"
I'm thick skinned (ok not true, but I think I have a layer of tephlon in there).
Situation 1:
In the car and Ella is singing a song about who knows what, but she's passionate about it. Zoe gets this face like she's struggling to keep the vomit down, when all of the sudden it comes out.
Zoe: Ella, Could you please stop singing... (she tried to swallow the vomit down) because... well... it's really annoying and no one wants to listen to you.
well, atleast she's being honest! NO!!! not honest, rude! Sometimes there's a point to shut up.
Situation last week:
Boy in my car playing. Girl gets in...
Girl: How old are you? (yes , this is the opening statement)
Boy: 7
Girl: hmmmm, well you're short. stand next to me. yah, I'm pretty sure you're too short to be older than me, maybe you're just dumb.
word vomit! REALLY!!??? there's only so much cleaning up I can do ... and about 90% happens in the car... maybe it's the rolling wheels making them sick, bumps, windshield wipers.
Has TV taught our kids this... have parents? I always tell my girls to be honest and to use their big girl voices if they have a problem (logic please) instead of whining and yelling stop... tell them what you'd like them to stop and maybe why... key point to use from now on: MAYBE why.
So, this birthday, I'm shooting for the unexpected: I'm shooting to reduce the amount of word vomit I have to clean up in my car! Good luck on your end... don't let it in my car!