Just to give an idea for people to better visualize this matter, the issue of Tasawwuf being a practical science is analogous [in the modern societies] to those institutions set up to organize and regulate society – there might be and there are problems in a nation’s police force, their labor laws, yet the existence of such laws, institutions, and procedures is absolutely necessary, without them the whole of society would collapse (for example, something like police brutality cannot justify the total elimination of that country’s police and army, the whole country would be ripe for chaos and invasion).
Likewise, the specific instances of some Shaykhs of Tasawwuf being accused of wrongdoing is one thing, but this is never to serve as a basis for eliminating the science. Likewise, there were so many weak narrators and even so many outright liars in the transmission of Ahadith; those who are biased against the Hadith corpus will use this as a basis to call for total dismissal of Ahadith, but this is obviously an incorrect attitude.
This attitude is incorrect even though only a percentage of the total Ahadith in circulation are considered to be authentic, yet the science is not to be thrashed, so one wonders why Tasawwuf would have to be eliminated in the minds of some due to accusations of wrongdoing, or the accusation that some practices are contrary to the Shariah. (Also note these are accusations, not all the things are as bad as the opponent makes them out to be, plus just like the Hadith-rejector, the Tasawwuf rejector is often biased to begin with, so no explanation or elucidation will suffice for him.)