Dismissing stuff as "just a theory" is a slightly more verbose way of saying "I'm dangerously retarded".
I don't understand how that is anything but wrong. Was it supposed to be funny, sardonic, or satirical? Maybe the person who wrote it doesn't know what a theory is.
Let me list some theories:
I won't get hit by a meteorite and die tomorrow.
A bunch of monkeys won't fly out of my ass.
The cereal I intend on eating in the morning is imitation coco puffs and not feces.
Every molecule of air around me won't randomly move away from me at the same time and I suffocate instantly.
Putting an irritated mongoose into my rectum is a bad idea.
I won't have a freak allergic reaction to a tarantula bite when one finally does bite me (it's inevitable in my hobby. It's considered an initiation if you get bit and keep going.)
Now here's the thing: You probably rely on thousands of theories every day when you go out and do things. Granted, some are bad theories. The theory I had a while back that Bacardi 151 and Ranch Dressing went well together was proven disastrously wrong. I modified my theory to not include Bacardi 151, and now my theory is that ranch dressing is okay, just in small doses.
But just because that was a bad idea doesn't mean I should run and stick a mongoose up my ass after slapping it around a bit. Saying that something is unworthy of your attention because it's "just a theory" is essentially a bunch of words that don't mean anything. It's similar to if I said something you didn't like and dismissed it as "just my opinion". Yeah, the fact that I said it proves it was my opinion, no need to point that out.
Saying something is a theory means that there is some way to prove it wrong. I could possibly get hit by a meteorite. It is possible for a bizarre set of circumstances to occur that would result in monkeys flying out of my ass. If you are going by pure scientific law, you literally have roughly 18 of them. (Depends on who you ask on that one, some scientists say there are more, and I'm not prepared to argue the point at this time). No matter how hard I try, I can't make gold from nothing. I will never make water that has anything other than two atoms of Hydrogen and one atom of Oxygen without it being something else entirely.