In relation to electrostatics, the Cavendish experiment does not involve electrically charging the masses.
In the video that I posted you can see that the experimenter does not charge the hanging lead blocks at any moment.
Discussion
They can't isolate objects from electrostatics, which means they can't prove that the effect is caused by gravity.
Seriously, I won't entertain this point any further until you watch what I posted.
Even if it was electrostatics, the moment the hanging blocks touch the sitting blocks the charge would dissipate and the electrostatic effect would vanish (the hanging blocks would move away). But that's not the case. They stay next to the sitting blocks.