The Mishna at Sotah 20a writes of a "plague" of perushim who bring destruction to Israel. Likewise the Gemara at Sotah 22b describes seven categories of perushim -- a word some translate as "ascetics" but which Soncino (unfortunately) translates as "Pharisees" -- very negatively. It is hard to believe that the sages are describing their own colleagues. Who are they describing? Could it be the Essenes?
The sages are bemoaning ostentatious charlatans. Bear in mind the term Pharisee did not necessarily refer to a fellow sage. It was a whole movement. The hebrew word for it does translate to ascetic.
King Yannai said it best to his wife after the gloss on 22b:
Rashi explains each type of charlatan:
Note that Abaye and Rava told the lecturer of this passage to omit the final two types of Pharisees, because Rav Yehuda in the name of Rav encouraged observance even with ulterior motive, because genuine commitment would eventually follow.
As an aside, the Jerusalemite Talmud brings the same passage in Berachot 9:5, in a different context. It is cited in the Babylonian by Tosafot in s.v. Parush. The Talmud seems to just be discussing the different types of approaches toward observance.
Yitzchok Isaac Krasilschikov explains each type:
The Talmud actually encourages the final two types of Pharisees, and says that Abraham was the most beloved of them all.