From the link above:
Critics of Arminianism tend to portray the Arminian view of election in this way: God elects to salvation those whom He knows will believe anyway, therefore election is basically meaningless. God's election is conditional on what human beings will choose to do: He just elects those who elect themselves--in fact, this view makes Him powerless to save anyone without their cooperation. The sacrifice of Jesus is not sufficient to save; it must be mixed with the individual's faith in order to be effective. The believer becomes his own co-savior and robs glory for salvation that is due to God. He gives himself a means of boasting, even though the Bible says to "let him who boasts, boast in the Lord."
The reason why the Arminian view is seen in this way is because of an exclusive focus on the individual. The Reformed view sees God essentially as electing individuals (say, Peter, Paul, and Mary) who together become corporately the people of God. Those who hold this view incorrectly assume that Arminians also focus on the individual, but merely get around God's election by basing it on foreknowledge of the individual's exercise of faith. Arminians, however, do not start with the individual. They start with the plan of salvation, centered on the sacrifice of Christ. The point of the election passages, says the Arminian, is the sovereignly and unconditionally determined criterion of election: faith in Christ for the atonement of one's sins. That criterion becomes the defining characteristic of the people of God. God's people are not the wealthy, or the intellectual, or the noble, or the strong, or even those physically descended from Abraham or those who strive the hardest to follow the Law. They are those who trust in Christ for their salvation. Period. Through the power of the Gospel we are enabled to believe; those who choose to do so become a part of that chosen people (which is what ελεκτοι means). But God's eternal decree is that He has chosen to choose those who believe, as opposed to any other group. That is unconditional and unchangeable.
It is only when considered on the level of the individual that foreknowledge even becomes an issue. Once God has chosen to choose those who believe, then He of course knows who that group will consist of as individuals. "General election" (the choice of a group, as opposed to "particular election," the choice of specific individuals) is sometimes ridiculed on the basis that if God chooses a group, He must necessarily choose each individual member of that group. But that is only true if one considers a group in a static sense--"My church consists of each individual member in it." However, a group based on a criterion is a dynamic group: the church may gain some people and lose others and still nonetheless be the church; it is defined by those who choose to worship together. God knows who will respond to the enabling power of the Gospel by choosing to believe (say, Peter, Paul, and Mary) and so in a sense He has elected those individuals for salvation, but it cannot be said that they "elected themselves," because they didn't choose the criterion for election.