It's a tricky concept...

I'm a pretty sensitive guy, but I tend not to show it. It's sort of a guy thing when it comes to appearing stoic. We still haven't really evolved out of the stereotype that boys and men are supposed to be tough. While it is progressing better these days, but for whatever reason it's still typically viewed negatively.
I think also a lot of guys (myself included) tend to be much more prideful than women.

Anyways, I think the average person may find dealing with some one emotional slightly distressing. They may not know how to help or that have their own issues so they don't want to have to deal with some one else's. Another possibility is that they are reserved on helping because if they do it once... there is a pretty good chance they will come back to you again. Think about it... if you were the person that actually decided to help, you would most likely to be the first that they will go back to. So they probably don't want to having to keep dealing with the person, probably because if they turn them down the next time they end up feeling guilty over it.

When it comes to some one telling you to calm down or relax... it depends on the person sometimes. For example say.. a co-worker tells you this. It's sort of a default response because they probably don't understand or are able to empathize with your situation. So the "knee-jerk" response is to just say to calm down or relax, because that's all they know that they can do. So for those kind of people, try the best you can to not take it personal. Which can be hard to do some times, believe me lol.
Now if it came from your husband... Hmm, well I don't know the circumstances so let me take a shot in the dark here. He may have told you that in hopes that if you are more calm, you would be able to better explain what the deal is. Maybe the reason he is so stoic about it because logically it doesn't make sense for the both of you to be stressing out.
I know it tends to drive guys nuts when their wife/girlfriend tells them "It stresses me out that you aren't stressed out!!" The claim that guys don't care. Personally, that's just an absurd argument. There's a huge difference about not caring and being calm about a situation. You should NEVER force stress on some one else just because you are.

But I suppose that is just my opinion.