I think your objection is fairly clear in terms of 1) you point out the difference between e.g. standing with a sign vs. more expensive options, and 2) you say "right to free assembly was to give richer corporations more sway."

Fundamentally it sounds like your complaint is that wealthy people are presumably more able to be effective with their efforts than folks who, e.g. can't afford as big of a bullhorn.

Citizens United wasn't about that. There wasn't a law saying no person shall spend more than $1k/yr supporting a candidate.