Like with many things in life, it is important to distinguish between "Tasawwuf" and between those who attribute to themselves to Tasawwuf (i.e. Sufis). It is necessary to distinguish between "Islaam" and between those who attribute themselves to Islaam (i.e. Muslims).
So what does that mean? It means that the actions or statements of a particular person should not be used as the criterion to judge an entire group. For example, a person tells you that he rejects Islaam. You ask him "Why?" He says it's because his neighbour, Zaid, is a Muslim, but Zaid is a drug-dealer who's corrupted the whole neighbourhood; therefore, he rejects Islaam. Is that logical? Not in the least. The actions and drug-dealing of Zaid are not representative of the Deen of Islaam. The Deen of Islaam stands on its own, independent from the actions/statements/behaviour, etc. of `Amr or Zaid, or any person who attributes himself to it.
It is the same with Tasawwuf. Tasawwuf (also known as Tazkiyah) is a branch of Deen - is that correct? So it is part of Islaam. What Tasawwuf entails is derived and understood from Qur'aan and Sunnah, not the opinions of people. Mere "opinions" - as in, "it's just my opinion (i.e. I don't have a shred of evidence for what I'm saying but I'm saying it just because I feel like it)" have
no place in the Deen. The Deen is based on
Qur'aan and Sunnah. Every branch of Deen can only be based on Qur'aan and Sunnah. If anyone speaks in Tasawwuf from his own personal whims and fancies, it does not affect or represent Tasawwuf. It's very important to understand this.
These days, you get a myriad of weird sects around the world who all lay claim to Tasawwuf, but as the true Awliyaa always say, such people are "highway robbers". The true path of Tasawwuf has been clearly demarcated. It's as bright as day. There are no "grey areas" or "cloak-and-dagger, Kabbalah type" ideas and practices.
Once this is understood, the mist surrounding Tasawwuf clears up instantly, and any condemnations the A'immah of the past and the Salaf had made regarding certain "Sufis" becomes immediately and easily understood. Those "Sufis" who were condemned were doing their own thing, outside of Qur'aan and Sunnah. They were innovating
Baatil ideas and practices into the Deen, and hence the Salaf condemned them. Condemned
them, not Tasawwuf/Tazkiyah itself.
For example, in India and Pakistan, one sect among the Barelvis called the "Naqshbandi Haqqanis" used to worship a certain "Peer" called Nizaam Haqqani (an absolute Shaytaan in human form). They used to put a picture of him up on the wall of their house, and they would make Salaah facing it, i.e. the picture as the Qiblah. These satanists also claimed to be "Sufis". Now, if the `Ulamaa condemn them and say that what they are doing is Kufr and Shirk, then this is not an attack on the pure, pristine Tasawwuf; it is an attack on Shaytaan and his followers who try to undermine it and transform it into something it never was.
Other false claimants to Tasawwuf, "pseudo-Sufis", entertain Baatil, Shirki ideas and satanic practices like believing the Shaykh has power over all things, or is all-knowing, or they eat the excreta of the Peer-o-Murshid as "Tabarruk" (to take blessings from it), or they make Sajdah to him, or they believe he can overrule the Sharee`ah, etc. These people have nothing to do with Tasawwuf, just like Shi`as, Qadiyanis, etc. have
nothing to do with Islaam. The Islaam of Rasoolullaah
صلى الله عليه وسلم and the Sahaabah.
Once again: distinguish between "Tasawwuf" and those who
attribute themselves to Tasawwuf; between Islaam and those who
attribute themselves to Islaam. The actions of the claimants to a particular group are not necessarily representative of that group.
It is narrated that Hadhrat `Ali ibn Abi Taalib
رضي الله عنه used to say - and this is a really amazing quote which people should ponder over:
إعرف الحق تعرف أهله, لا تعرف الحق بالرجال
"Know the truth and you will know who are the people of the truth. You will never know the truth from the people."
والله تعالى أعلم