That is a diversion, along with the others.
We all know that radical Islamists exist and murder people who try to exercise their free speech rights. The point is, will society ever get to the point where there can be some Muslims who don't go around murdering people joining Christians who don't murder people getting together for a march and celebrating free speech as shown in the OP?
There should never be such a march.
You are getting these replies because it is you who have missed the point.
The point of "Je suis Charlie" isn't that you can't be angered by sacrilege. It's that your anger doesn't justify murder. As an agnostic leaning more toward atheism, I am actually offended at some of the anti-Christian blasphemy on Charlie Hebdo's covers. Some of it is genuinely vile, whatever your affiliation. [And was deliberately printed to offend, which was the point of the authors.]
Piss Christ is also truly vile. I would not march in support of Serrano per se under any circumstances. But I would march in defense of his rights.