The concept "argument" presupposes you have freewill so its circle, self-contradictory non-sense to "argue" that it is an illusion.
Edit: for clarity
Edit: for clarity
If freewill is an "illusion" then "argument" is a hollow concept as well. If we don't have a choice in what to believe then what is the point of arguing?
The essence of your position is that you are trying to convince me to change my mind and agree with you that I do not have the capacity to change my mind. It is a self-contradiction, as all forms of determinism are, and if you were consistent with your belief you wouldn't be arguing at all, yet here you are. I think (beyond a certain point) denying freewill is an inherently dishonest position but unfortunately you have plenty of company.
(Just explaining, personally I consider the question of free will to be a non-question.)