Here is a good post that looks at some of the major difficulties in Calvinist accounting of free will and choice (below), It also does a good job concisely pointing out how Irresistible Grace is indeed coercive, even on some Calvinist definitions:
The Coercion Problem
First, the Sproul-Edwards account of choice implies that God’s giving irresistible grace to the elect is coercive. To be sure, Sproul does say that it is a “misconception of irresistible grace” (122) to think it involves people being coerced “kicking and screaming against their wills.” Rather, they desire Christ because God “plants a desire for Christ” (123) in them.
Unfortunately, that’s not Sproul’s definition of ‘coercion’. For him, coercion involves “imposing choices upon people that, if left to themselves, they would not choose” (57). And in fact God does that to the elect. For God imposes an irresistible desire on the elect (for Christ), and as Sproul says “our choices are determined by our desires” (54). Therefore, God imposes choices on the elect by imposing irresistible desires on them. Moreover, these choices are ones they wouldn’t otherwise have made, since apart from irresistible grace no one can choose Christ.
So both the elect and non-elect are coerced in their “decisions.” And if we know anything at all about free choices, it’s this: they’re not coerced. Caused, perhaps; but a free coerced choice is a contradiction in terms.