I absolutely promise you that there is a SEVERE, DRAMATIC difference in the mouse interpretation between OS X and any version of Windows.
If you honestly feel like you want to argue that it's the paranoia or projection of the person(s) making the claim then you need to sit down with the two side by side and compare them. Try actual grown up, quick, precise movements. If you do not immediately notice the measurable, explicit difference in the interpretation than you are either oblivious or not using a mouse as quickly and fluidly as you could be ( on Windows ).
This is so real that Apple has received hundreds if not thousands of emails begging for a correction or optional disabling of the "acceleration" in the admin. There are a handful of programs intended to solve exactly this issue, and all fail ( though they also all help, just not resolve the issue completely ). There is even some kind of electronic petition that mac lovers started to get Apple to listen.
It's absolutely crippling for any advanced mouse-based interaction with the computer. It's embarrassing how some mac users are so blind and defensive that they immediately turn someone trying to solve an obstacle in their experience into a personal attack on that person's motives or character.
OS X has an entire glove compartment full of usability and interaction issues. People that actually are well-versed with the OS and its alternatives will be the first ones to admit to / proclaim that.