You do not understand reformed doctrine, so when you say something like this it just shows what you do not know..
Men DO HAVE a "free will" , but it is God that sets the parameters of that freedom.. man can only choose from the set of choices before him..
It is God that chose your family (your genetics if you will), God chose your sex, your nation of birth , your educational choices were determined by you sex.IQ, nation of birth, place of residence, family income etc..God gave you choices BUT He set the expanse of those choices.
You can not choose out side of them. You can not make yourself into a genius or change your race or family financial situation..
It was God who determined your genetic makeup.. He placed in you a preference for corn over cauliflower, He knows when faced with that choice what you will choose because He ordained that preference. He gave you a preference for blue over green, He knows that given a choice what color you will choose , because He ordained the preference.
God knows every sinful preference we have because he did not or does not or will not restrain it.
So God knows if you have a preference for porn, that He Himself does not restrain you will choose that sin.
Natural man is no longer made in the image of God..(Although we retain a semblance in some respects. After the fall man was begotten in the image of our natural father Adam (see gen 3)
Adam, made in the image of God could choose to sin or not to sin, after the fall, man lost the ability not to sin... everything he did was sin before God, because the relationship was broken. God made a way for man to deal with that condition on a temporary basis with the blood sacrifices that man could cover his sin with.
That of course was a type of Christ..
A man that comes to Christ in faith, regains his standing with God..He now can once again choose to sin or not sin.
As has been discussed earlier, man is no longer the servant of sin, but a servant of Christ and because his heart and mind and will have been renewed, born again, he now hates sin and chooses grace..
This man is not perfect or sinless, he still can fall to the flesh, but he now HATES the sin, he no longer loves it...He knows he now has an advocate with the Father,Christ.. His new will desires to repent and turn from his sin
So you see yes, a saved man can and does choose sin sometimes.. but we hate it and rebuke it and repent before God, because it is a burden and a barrier to a full relationship with God.