If kids or teens are getting yelled at by guardians, is it really that normal for these kids and teens to get nervous in this situation?

In my experience, being nervous or upset when getting yelled at or talked down to isn't a choice, it's a reflex. No matter how hard you might try to act differently, there are a lot of emotions that are triggered in these situations, and it is nearly impossible to suppress them. I would say that it is absolutely normal, so long as it is not in outrageous proportions (having a meltdown everytime a comment is made or freaking out on a regular basis) even an occasional tear i would say is normal, tho the guardian should try to combat this by making more gentle aproach 

Define “this situation”  what situation exactly is that?

some people scream bloody murder on a roller coaster and some people laugh hysterically. some people might get nervous when being yelled at while others might be completely unmoved. 

Just report the repeating troll

Define “this situation”  what situation exactly is that?

I think it would be normal to at least be a bit nervous, especially if the guardian is abusive. Also, many children wish to impress their parents.