It would be somewhat true for him to say that, because Dooku was part of the Jedi order, and even though he is no longer with them he still views them as colleagues. He just thinks they are on the wrong side and have lost there way. He isn't an outright Jedi killing Sith, and he wants to correct the problems of the Jedi so he kills the ones he has to, the ones who would not reason with logic. He never once killed a Jedi out of anger or rage. If he didn't have to and could save one he did. The ones he did kill he killed, because he cared for the Jedi order and couldn't get them to see the problems of the order and how to fix them.This is why Dooku is so tragic. He still respects the Jedi Order and the Jedi, and wants to see it done right by so for him to call them "friends" is kind of touching.
At the risk of being over-the-top, I think this is exactly what Dooku wanted the Jedi to believe about him, not what he really was. He reveals himself when he says the line "I've been looking forward to this." Not very Jedi, or friendly towards former Jedi companions, I thought, to relish a lethal duel where somebody's got a good chance of getting a hot bar of plasma through their gut. Dooku was a Sith, and the Sith always have two metaphorical faces: the public one, and the real one. See Palpatine/Darth Sidious for details, and indeed the fact of Dooku's dual identity as Darth Tyranus. Yoda says Dooku's ways are now "Lies, hatred, greedy mistrust", and at the end of Ep 2 he was about to cold-bloodedly execute Obi-Wan, down and defenceless, until Anakin intervened.
Dooku doesn't strike me as a tragic figure -- deceived, yes; seduced by the Dark Side, yes; but willingly taking that course because of his own cult of personality. The way Matthew Stover 'writes' Dooku in the novelisation of Ep 3 (EU though it is) to me gets the character perfectly: Dooku is the archetypical sociopath. He believes other people aren't quite real, and can only class an individual as either an asset to him or a liability to his goals. He is an example of Jedi detachment taken to a cruel extreme: a detachment so profound it leads to disregard for human life at all. His pride and overdemanding standards have metastasised into a condition so easily seduced by the Dark Side that even decades of training as a Jedi Master couldn't prevent it.