@Snel : and not all hadith are ghair sahih as well. Moreover, what you say is not confined musnad ahmad only agree but all sufis aren't wrong. you mean once they were Muslims but later on they left Islam..? Can you write their names and source from where you've got all this? you mean, since the embracing Islam they had no correct aqida but they are likely to be deviants No, probably, it's apostasy agree.
I didn't say all of them were not sahih, but collections such as Sahih Bukhari and Sahih Muslim are more reliable in this regard, as it's generally assumed that everything within those are sahih.
Regarding the sufis: If some of them are doing things right and are not engaging in any bidah then why do they feel the need to put this label on themselves? And furthermore, by doing so they are also associating themselves with people who believe in things such as pantheism. They then call themselves "sufi muslims" (allegedly a perfect subset of muslims) and consequently include people like the pantheists within the fold of Islam. This is not something a muslim can accept. You should also consider the fact that neither Muhammad nor his companions called themselves "sufi muslims".
And you wanted a name of someone who left kufr sprinkled with green moon-crescents to one that isn't. Sure, how about Nabeel Qureshi, the christian apologetic who's also a friend of David Wood? He's definitely not an apostate from Islam, as he never was a muslim to begin with. He was previously an ahmadi.