The sticker "evolution is a theory, not a fact" is misleading. It suggests that theories somehow graduate to becoming facts, and since evolution is a theory, not a fact, this somehow diminishes the validity of the theory. It doesn't. 'Theory' is as high as it gets.
How about "gravity is a theory, not a fact". Sounds ridiculous, doesn't it?
Yep, I was taught the theory of gravity in school. The teacher brought a ball into the room and dropped it. It fell to the floor. Been waiting for a likewise demonstration from evolutioners but they keep telling me that a birth defect is a transitional form. 
Gravity sure does pull down hard on my bunns---gonna have to do more research on your question----
Like the Theory of Phlogiston? How about Holberg's Theory of the Hollow Earth? I could name a lot of theories generated by scientists that were subsequently disproven, some of them after being believed for a long time.
To observe and report data is one thing. To assign reasons for that data is another thing entirely. Kepler was a terrific astronomer, but he was out to lunch with his Theory of Epicycles.
Speaking of ridiculous, are you actually claiming that calling a theory a theory diminishes the validity of a theory?
Speaking again of the ridiculous, one can perform tests to prove the validity of the theory of gravity (jumping out the window is an all-time favorite). One can not perform tests that prove life sprang forth from nothingness and all current life forms evolved from one or many life forms that spontaneously sprang forth from nothingness
If "science" can no longer handle calling a theory a theory then we need to stop calling this activity "science"