2 Pet 2 and Jude are very similar, both in structure, language, and themes. These two are parallel passages (cf. e.g. this site):
Jude 8-9: Yet in like manner these people also, relying on their dreams, defile the flesh, reject authority, and blaspheme the glorious ones. But when the archangel Michael, contending with the devil, was disputing about the body of Moses, he did not presume to pronounce a blasphemous judgment, but said, “The Lord rebuke you.”
2 Pet 2:10b-11: Bold and willful, they do not tremble as they blaspheme the glorious ones, whereas angels, though greater in might and power, do not pronounce a blasphemous judgment against them before the Lord
In both contexts, "doxa" is translated "glorious ones" (ESV). Quoting an extract from Bauer's Lexicon, "4. a transcendent being deserving of honor, majestic being, by metonymy (cp. Diod. S. 15, 58, 1 of citizens who stood out from among all others in offices and honors) of angelic beings (s. Philo, Spec. Leg. 1, 45; PGM 1, 199) do/xai majestic (heavenly) beings Jd 8; 2 Pt 2:10 (s. also Ex 15:11 LXX; TestJud 25:2.)"
Basically, Bauer is saying that the word can refer to angels, but also to any glorified being, including humans.
But look at the verses in question as quoted above. Peter says that angels do not pronounce a blasphemous judgment against them (referring back to the glorious ones). The parallel passage in Jude says that Michael, an angel, did not pronounce a blasphemous judgment against Satan. Thus Satan in Jude is the same as "them" in 2Pet 11, which refers back to "the glorious ones". Satan, therefore, is one of "the glorious ones". But Satan cannot be alone in this group, as "glorious ones" in plural. Neither can this group include non-fallen angels, because these are "greater in might and power" than "glorious ones" (2Pet 2:11). It is natural, then, to group Satan with the fallen angels, and say that Satan and demons are the "glorious ones" referred here. Their "glory" may be that of strength, power, capabilities, created order, etc.
The final question is, "How might false teachers speak evil of or pronounce a blasphemous judgment against Satan?" Before I suggest an answer, note this: "Blaspheme" is the translation of "Blasphemeo" (Greek), meaning "speak evil of, slander". The word is used both of speaking evil against God (Mt 9:3) and against men (Tit 2:3, Rom 3:8).
Jude says that Michael did not presume to pronounce a blasphemous judgment against Satan, but said, "the Lord rebuke you". This is in contrast to what false teachers do. I believe, therefore, that it is fair to assume that false teachers in this instance were saying of Satan/demons, "I rebuke you" or something similar. Having been in unbiblical churches a great portion of my life, I can confirm this. Technology and society may have changed, but false teaching as described in the Bible retains the same characteristics. It is not uncommon in certain churches to hear someone "binding Satan" or commanding Satan to do this or that. The same with demons. But when Michael the archangel did not take it upon himself to judge or command Satan, who are we to do so?