I'm not sure how people think they can, or are entitled to tell you what you should do with your life. Sure, opinions are fine, but putting someone down is another story. I remember that there was once where I told someone that my dream was to go to America, and that person responded with, "I'm sure there are better dreams than that?"
First off, WHO gave you the permission to say that my dream is lacking? It's MY dream, not yours. If your dream is to get fucked up the ass with a big black dick, that's your problem. Mine is to go to Los Angeles, California. Now buzz off. And secondly, how would you feel if I said that your biggest dream was shitty?
1) It's not okay to put other people down.
2) It's not okay to put other people's parents down, no matter how much they hate them. If it's their parents, then leave it to them. They're not your family.
3) It's not okay to tell other people that their dreams suck.
I understand that there are dreamers and realists in this world - but even realists have dreams. If you think your dream is better than other people's, fine. So be it. But don't say it to them and degrade someone else's dream because everyone's dreams are DIFFERENT. You might want to be an astrophysicist, I want to go to California. How do you even compare these?
Do not even make a disdainful face. Encourage them. Even the smallest bit of disapproval can feel like a huge rebuff and it's not easy to recover from that. It takes a long time to build up a dream, a goal, but only a few seconds to smash it. Don't be that asshole who has a cactus somewhere the sun don't shine - no one likes those kind of people.