I’ve learned a few of these “shutdown” comments over the years, unfortunately. There are a few things you could do. You could 1- redirect the criticism onto the person making the comment. Call them out. Something like, “it’s not kind to criticize your grandson,” “you should be more supportive of your grandson and less critical; don’t you think?” “He needs your love and support, not your snide comments.”
2- Passive aggressive guilt trip : “ It’s shameful the way people expect so much of kids these days, isn’t it? Kids have it hard enough without having to worry about acting a certain way or criticism for being something they aren’t. It’s really hard on their mental health. I really wish more people would consider how hurtful their words are.” “kids these days have it hard enough. They need loving parents and grandparents, not more criticism.”
3- Counter the comment, and stand up for him- “He’s acting so mature for his age! Many boys his age would be trying to show off and act stupid in front of those girls. Don’t you think his behavior is impressive? I am so proud of him!”
I found that the more i stood up to those kinds or comments made by people in my family, the less often they made them. Best of luck!
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.