That's not the only problem: If you have a small pull-up resistance, then in the case of overvoltage unsane currents are driven onto Vcc, which cannot be absorbed by +5V regulator very probably: If the current driven onto Vc is bigger than all the supply currents sourced by the regulator, the regulator goes out of control and Vcc begins to rise.

So, although a low input impedance would be the best cure against charge injection due to capacitive stray capacitances, this low impance should not be referenced to Vcc.

Kai