Sorry, that is simply wrong. It is a fact that certain germs cause certain infections. It is a fact that when you drop something it falls. That is why it is called The law of gravity not the theory of gravity.
Scientists and mathematicians recognize that there are laws and there are theories. Laws are not disputable. Theories are possible explanations for events. They can have strong support, like the theory of relativity, or weak support like the big bang theory. They may have passionate supporters and passionate detractors.
It is, however, ill advised for passionate defenders of evolutionary theory to adhere to that theory in such a way as to appear to be mystics defending their faith.
Many creationists like to ignore that because it makes "evolution is only a theory" sound like a more meaningful statement.
As I have demonstrated, the word theory is not identical with proven fact, generally referred to as law. And therefore the statement that evolution is only a theory is a meaningful statement.
Most everything in science can be proven through experimentation and observed with the eyes. Evolution cannot. Evolution faces the same problem creation does, it cannot be observed, therefore other options should be explored, but all to often they are ruled out as non-science. Is this not a grave error on behalf of science?
This is basically BS. Evolution is not a theory in the same way as other areas of science, because all others that I'm aware of are based on repeatable experiments with measurable results which can be used to confirm or deny the theory.