I voted "yes", but it isn't that simple.
I feel Sharpton on a moral level shares part of the blame for those murders, but not from a legal standpoint. The reason I say that is because he stoked the fires of racial anger and did so under false pretenses. He went to Ferguson and instead of being the voice of reason and telling the community to wait until all the facts were known, he willingly embraced the unsubstantiated, unproved (and ultimately false) "racist cop kills unarmed black teen" narrative and encouraged black people to take to the streets. Thanks to him, people across America falsely believe that the catch they've heard and seen from politicians, athletes and celebrities "Hand up, don't shoot" has some basis in fact, when it doesn't. It has led to a lot of racial animosity, hatred and anger toward police across the country for doing something that they never did.
What makes matters worse is, even after the facts were known, Sharpton never set the record straight and continued to encourage people to take to the streets and voice their anger.
He is a leader in the black community who for some unknown reason, is listened to and revered by black people across America. With leadership comes power, and with power comes responsibility. Al Sharpton acted irresponsibly and abused that power, and in my opinion that makes him partly responsible for not only the murder of those 2 policemen, but responsible for the millions of dollars in damages and lives that were ruined in Ferguson.