Very challenging sentence, but here you go:
--not to be on any account compared with the noble fellows who fill the Volunteer corps--
the punctuation "--" indicates where it starts and ends. So, what you asked about "fill the Volunteer corps--pot-house heroes" is not together.
Some of the British section, those tremendous patriots who demonstrate but do not fight *** pot-house heroes, and others of that kidney, had just distinguished themselves by mobbing Mr. Schreiner in the streets.
Now, a pot-house is a (drugname)-house. You'll find several "houses" where the name is typically illegal drugs because it is extensively used or grown/manufactured there.
So while this excerpt speaks highly of the volunteer corps, the others are apparently terrible people.
May I ask what you're reading? It sounds interesting!