With X is similar to Y, X and Y are both nouns or noun phrases, not independent clauses.
Independent clauses have their own subject and verb. Words ending in "-ing" aren't verbs unless have or be is before them - they are nouns or modifiers in that case.
You might think "Dave's" is the subject in the phrase "Dave's rebellious act of escaping from authority control" but it's a modifier expressing possessive case, not a subject - it qualifies who/what "act of escaping" belongs to. The entire phrase "Dave's rebellious act of escaping from authority control" is the subject of is.
The second phrase "that of oppressed citizens defend themselves against government tyranny" is the "target" of is (technically called a "subject complement" I believe). So you haven't started a new clause yet, you're still completing your first sentence. Another clue: the word of - the "object" of of has to be a noun.
So you must change defend to defending.
There's a couple common conjunctions (and, but, for, or, nor, so, and yet) and marker words (however, also, consequently, furthermore, however, moreover, nevertheless, and therefore) that indicate you are probably working with at least independent clauses. See this page.