That's just not true, though. Leftist political authority is about overthrowing the dominant existing authority (formerly, feudalism, today capitalism), and replacing it with something where whatever authority remains derives more meaningfully from the people governed. Marxism-Leninism was a strategic philosophy about using as much authority as necessary to prevent counterrevolution; Lenin's writings specifically refer to the state "withering away" as it is no longer needed to defend the revolution. Of course, in practice, the need to defend the revolution never ended, which meant the state could never wither away, which is, I'm sure, how a lot of Soviet bureaucrats liked it. On the other hand, there was never any shortage of criticism of Lenin from the left, starting with Luxemburg (supportive but critical) and Makhno (actually fought the Red Army) to Trotsky (more critical than supportive, killed by Stalin's agents).
I'd also note, with regard to your example of "red flag laws", that actual leftists are much more supportive of gun rights than liberals. Look into the John Brown Gun Club or the Socialist Rifle Association if you're interested.