Here's the referenced video from Trump...
So, here's the argument we're hearing from the right wing... "Trump makes these same movements when he is making fun of people who are not disable, like Ted Cruz. Therefore, he is not mocking the disabled reporter." They often go on to acknowledge that Trump is rude, but state emphatically he is not guilty of mocking a disability.
I find that one of the most ridiculous defenses I have ever heard. Let me give a parallel example. If I called someone a "retard" who did not have a mental deficiency and then turned around and called someone who was intellectually challenged a "retard" would that mean I wasn't making fun of their disability? No. Indeed it would be worse because in the first instance, where I used that slur against someone without a disability, I was holding up the disabled person's condition as a slur. The intellectually challenged person becomes the living embodiment of the slur.
That is precisely what Trump was doing when he used the same movements in mocking Cruz. He was saying "Cruz is comparable to one of those people who are worthy of disdain and mockery." That he used the same movements when mocking someone who actually has a disability does not make it less offensive. Indeed, it is more offensive.
There are no excuses. That behavior clearly sets an example for others and normalizes behaviors that are despicable.