Adam Clarke on Jude 1:10

Speak evil of those things which they know not - They do not understand the origin and utility of civil government; they revile that which ever protects their own persons and their property. This is true in most insurrections and seditions.

But what they know naturally - They are destitute of reflection; their minds are uncultivated; they follow mere natural instinct, and are slaves to their animal propensities.

As brute beasts - Ὡς τα αλογα ζωα· Like the irrational animals; but, in the indulgence of their animal propensities, they corrupt themselves, beyond the example of the brute beasts. A fearful description; and true of many in the present day.