The comments number about 30,000. I have searched online for other reports or commentary relating to this Colbert episode, but haven’t found anything remarkable.
		
		
	 
Your comments seems to be saying "there are bricks in the wall."   Yes.  That is true.  What did you note in the predominantly negative comments on that video compared with the other Late Show episodes comments?   That was my point as stated before.  The fans were hugely turned off by the attack.  It's plain for every reader to see instantly.
And the votes shown below the video reflect 40% disapproval by viewers voting.  The normal for the Late Show averages less than 2%.  The data is unscientific, but it isn't hard to merely compare other YouTube recent episodes to see a clear spike. 
	
	
		
		
			What percentage of The Late Show viewers do you imagine fall into this category?
		
		
	 
I didn't imagine a percentage.  I know that both Jon Stewart and Stephen Colbert have noted it in the past when interviewed about their roles in infotainment.
	
	
		
		
			Would you be more or less content if the late night comedy shows were equal in their parody of all candidates? IOW, Is it ever okay to invoke humor to portray political candidates – or should comedians be expected to refrain from political satire entirely, for risk of upsetting some viewers?
		
		
	 
I would.  If all the show does is skewer either politicians nonstop, as a broad lampoon with individuals from across the spectrum, then fine.  It's just shit entertainment like stand-up comedy or night club humor.  People go out and listen to total crap from stand-ups.  
And it can even be partisan. If The Late Show or something from Fox just spends all its time tearing down the opposition, then it's clearly just a propaganda tool to pump out biased shlock against the opposite party or philosophy.  It's not particularly good satire or credible if it's tediously repetitive, but it is what it is. 
What Colbert did was hypocritical.  While taking dead aim night after night at the right, often attacking them for lack of inclusion, for anti-feminist positions, and for not upholding the poor, it then turns and attacks one of the elected officials who has been at the vanguard of all of the civil rights, as well as all his other positions.  And, in mocking him not based on his substance, it appeared a desperate attempt to undermine his credibility as a candidate.  
When considering Sanders' high ranking among the announced DNC candidates, the concerted and coordinated attacks by the media on the left make it obvious they favor the other candidates.  None of the other front-running DNC candidates have received the same negative attention.  None. 
It's kingmaking. And the pundits are not afraid to kill the princes in the tower to ensure the right heir sits on the thrown.