It seems this is a perennially confusing issue for many, so I wanted to do a quick vocabulary check on the word, theory.
For most people in a non-scientific context, when we say that word, we mean this:
That's all well and good, but it's important to remember that the above definition no longer applies when speaking in a scientific context. When discussing matters that are scientific in nature, theory means this:
Scientific theories aren't just "ideas"...they're time and science-tested explanations for why the world works the way it does. There is a veritable crap-ton of evidence for them. It is ignorant and irresponsible to speak about them as if they were merely some random person's flimsy thought. Essentially, when science says something is a theory...it means it's real.
I hope this makes things more clear...and if it doesn't, take a gander at the links below for further explanation. Have an awesome, science-y day. :)