Mark Zuckerberg is criticizing people for wanting to build a wall to keep illegals out. Remember that he was the one who bought the homes of his four closest neighbors for $30 million, so he could have more privacy.
To illustrate his hypocrisy, here is the pedestrian gate in the wall that surrounds his home:
Here is the vehicle gate into the walled complex that contains his mansion:
and here is a shot of the wall that surrounds the property. Note that here, the wall is backed up with a temporary construction wall, put up as his home was being renovated.