I think that's facile and actually downplays Fascism: It fits only if you drop so much detail that it's no better than saying "Crime Gangs are Feudalism" or even "Crime Gangs are Government".
While there may be a subset of gangs which also have Fascist ideologies, I don't see how one could claim all gangs express stuff like (among other definitions) palingenetic ultranationalism.
Fascist ideology, or goal is that we should be governed by a hierarchical power-structure not elected by democratic elections.
I believe most crime gangs fit that description.
On the other side groups who explicitly identify themselves as Fascist or Neo-Nazi etc. don't really differ from criminal gangs much. They have similar goals: Rule by the Boss, not restricted by any laws or elections.
While there may be a subset of gangs which also have Fascist ideologies, I don't see how one could claim all gangs express stuff like (among other definitions) palingenetic ultranationalism.
https://en.wikipedia.org/wiki/Palingenetic_ultranationalism