He has the power and ability to abuse the flagging feature to silence anyone he feels like.
He does not have that power or ability; nobody is silenced as a result of flagging—by anyone, regardless of their SP. Your posts go through as normal. Nobody on steemit can silence anyone else.
You're being somewhat disingenuous, as you are silent no matter how loud you scream if no one can hear you. Posts from accounts with negative rep are invisible.
Screaming into a void.