Rom 10:21

But to Israel he says: “All day long I have stretched out My hands To a disobedient and contrary people.” - Rom 10:21

The attitude of God in this scripture is that God makes a genuine offer to people, who reject God. If even a single one of those people fail to eventually get saved, then this genuine offer was made to more than just the "elect." 

If this one person does not get saved, but the offer was made to him, then this person could have gotten saved - otherwise the offer was not genuine.

And if so, man's choice is factored into the equation.

The  point is not

"Are you making man's will more powerful than God?"

but rather, 

"Are you making your ideology greater than God's plain statements in God's Word, and rejecting God's own Word?"

God has exalted his word higher than his name. 

I will worship toward thy holy temple, and praise thy name for thy lovingkindness and for thy truth: for thou hast magnified thy word above all thy name. - Psalm 138:2

Example:

Peter's opposition to Jesus' going to the cross, certainly was in line with the Calvinist opposition to the idea that man could choose to reject salvation. Both are justified by the claim of seeking God's glory.

In fact, Peter's act was even more so - this was not the rejection of God's offer that is being dealt with, but the death of God himself in the form of flesh! 

The argument of Calvinism is that making man able to choose, makes man greater than God - however, men actually killed God when He was manifest in the flesh, which no Calvinist will want to deny (I hope). Did this death of Christ by men - by sinful men - demonstrate man's superiority over God?

If not, then neither does God's ordaining for men to be able to choose 1  demonstrate man's superiority over God.

One might argue,

Well, the crucifixion was part of God's plan.

The proper response to that is,

Man's choice of rejecting or accepting salvation was part of God's plan.

• 1the ability to accept or reject God