There are some people who are just born, and remain obnoxious all their lives.
They ALWAYS have to make a nasty comment. Or point out something mean, even if everyone knows it and sees it and is aware of it. Count on the petty nasty person to feel the need to express it, verbalize it. This kind of individual probably has a sense of humor, lots of friends, and isn't overtly mean. Just the "shtuching" type.
Like when you are in elementary school, and she announces to the class, "I want to give the Bigmouth Award of the year to XXXX because she clearly wins it in this class!" ha ha ho ho. Let's embarrass someone and see if they laugh at being the butt of your jokes.
But sometimes as this person grows up, they become more subtle. You know the type, don't you? Like, they see you when you are 6 months pregnant and showing, and they say (at a bus stop or on line at PTA), "hey, mazel tov! Now I understand why your daughter told us every Sunday in carpool that you vomit every morning! B'sha'a Tova!". The truth is, people don't know how to react to this.
They enjoy pointing out embarrassing situations, minor faults in your children, etc. etc.
And thankfully, for every stupid person like this, there are handsful of polite, nice, thoughtful individuals who may THINK "about time she put on maternity, she's been green and gagging for four months" but they just focus on the positive and say, Abigezunt!
But perhaps it is healthy to meet up with a person like this every now and then. Because you walk away thinking more carefully about how to talk to people. And thinking about what NOT to say to someone.