What is their stance towards the protesters? Are they considered by the protest movement "part of the system" or do they have some credibility...?

Here the local stalinists are disapproving of these "petty bourgeois" movements that "draw attention away from the class struggle". No. Seriously: KKE said that about Spain, quoting these people, approvingly.
The non stalinist radical left (SYRIZA antarsya to its left, some sort of maoist-trotskyite mix, and the Anarchists) however are pushing the story like crazy, mumbling things like "we're next, eh?" and admiring the fact that the protesters have managed to contain violent groups so far (?) (the MS tv stations have not said a word about these protests so far AFAIK, indicative of the sort of editorial censorship that passes for news here).

These Egyptian reactions I found moving BTW:

The road of excess leads to the palace of wisdom - William Blake