Whenever I go to (or see on TV) a sad or romantic movie, I always end up laughing. It drives people around me insane, but it seems the more serious things get (like if someone dies...) the more I laugh about it. I want to change but I just can't. Sometimes the things are so ridiculous that I can't help it, like during really cheesy romantic scenes in, say, the notebook.
Also, I always laugh when batman first speaks in "The Dark Knight" and when Harvey Dent yells "SAY IT!!" in the hospital.
Is this normal?
Your companions make take this stuff more seriously though, so they have every right to be upset. Respect their feelings and you won't get badgered.