Post Ban

Fixed.

app.post('/user/ban/:userId', function(req, res){
    req.user.bannedReason = req.body.bannedReason;
    req.user.banned = true;
    console.log(req.user.id)
    req.user.save(function(err) {
	  if (err) {
	    req.flash('info','User banned:' + req.body.bannedReason);
	  } else {
	    req.flash('info','User cannot be banned');
	  } 
          res.redirect('back');
    });
});

Optimal

app.post('/user/ban/:userId', function(req, res){
    var user = req.user;

    user.bannedReason = req.body.bannedReason;
    user.banned = true;

    user.save(function(err) {
	  if (!err) {
	    req.flash('info','User banned:' + req.body.bannedReason);
	  } else {
	    req.flash('error','User cannot be banned');
	  } 
          res.redirect('back');
    });
});