why be negative when you can be positive. If you see someone do something dumb just ignore it (unless it’s especially funny then you can share it with friends another time).
We only live once so best to focus on the positives. When you’re nice to others you feel much better yourself. And everyone’s constantly learning, making mistakes anyway so while other people may seem uninformed sometimes, you also will be at points and you wouldn’t want to be ridiculed for that.
As for others being negative, just nod along and ignore. Or try to change the topic.