What do you make of Voltaire's constant jabs at people who crossed him during his life? Do you think it diminished the work in anyway?
This is a great question, but I have one in return: can you read Candide not knowing that Voltaire was lampooning some of his specific contemporaries?
All satirist did this: Alexander Pope is a prime example — in fact, most of the English Neo-classicists (and French, for that matter) made this a regular aspect of their works. However, the fact that we still read these works today suggests that these types still exist, that they contain seemingly universal qualities that allow contemporary readers to relate. We have all been swindled, criticized, and hurt by self-centered folks around us; we don't need to know the specifics of Voltaire's life to find we understand why he derides and rails against certain human foibles.
Along the same lines: consider Virgil's Aeneid. Many of Virgil's contemporaries criticized him for writing a state-sanctioned piece of propaganda. Aeneas can be seen, especially in the latter part of the epic, as little more than a mouthpiece for Roman values, particularly duty to the state. However, does knowing this probably fact diminish the greatness of Virgil's Aeneid?
Like the Aeneid, we still read Candide for what it says about our culture, even without the knowledge of Voltaire's particualar grievances.