Jesus knows them as He knows all men.

Joh 2:24  But Jesus would not entrust himself to them, for he knew all men.

“the love of God” = can either denote love from God or love for God. Here it is undoubtedly love for God; these men had no real love for the Father and Jesus knew it. It is interesting that this phrase can mean either of the two things since both are connected. God loves us and His love for us is not based on any merit on our part. We see the extent of His love for us in the cross. But God’s love is also creative in the fact that it illicits a response of love within us. When we experience God’s love for us, we in turn love Him back. 

1 John 4:19 We love because he first loved us. 

Westcott states it another way: “God is at once the Author and the Object of this love.” (qt’d in Morris p.332)

Sadly, the Jews thought they did love God. They knew the commandments and were strict adherents to them. They were fully aware of the command in

Deut 6:5 Love the LORD your God with all your heart and with all your soul and with all your strength.

and professed to keep it, but in fact there was no real love for God in their hearts. If there had been, they would have loved and followed the Son. The Jews had not started with the love for God and then sought Him to determine what He desired of them; they had worked out their own religion based on God’s commands and then tried to fit God into it. Barclay says, “They did not really love God; they loved their own ideas about God.” And Milligan and Moulton state that, “They valued themselves on what they presented to Him, and yet they presented not that which most of all he sought, – the love in which self is lost.” (both qt’d in Morris p.332)