Past participle as adj

I'm having a disagreement with my boss (a non-native speaker) who says that in this sentence the word "rigged" is a be-verb. I say it's the past participle acting as an adjective and I confirmed it with two other native speakers who have writing/editing experience (one even majored in linguistics and has two MAs in teaching to other languages). But my boss insists that it cannot be an adjective and can only be a verb and it shares the preposition "by" with "driven" but the agent is unknown.

I argue that if it were to share the preposition "by" then the agent is "greed" and yet "greed" can't "rig" something. However, I am struggling to find appropriate sources to prove either case. Here is the sentence in question:

"Cynics will tell you that everyone is selfish and weak, that the system is rigged and driven by greed, that you can never succeed, so it's pointless and contemptible to try, that all ideals are ridiculous, and the do-gooders are only out to show off their own supposed virtues."

I won't comment on rigged as a "be-verb" because that term means absolutely nothing to me.

However, it's the and which is causing the problem, and my intuitive response is that your boss is right. The and means that rigged is to be considered with driven. Using brackets to define components of the sentence, it's

The system is [rigged and driven] [by greed].

Here, rigged and driven are both past participles functioning as adjectives. Both are describing "the system". Because they are both exactly the same part of speech, with the same qualities, joining them together with and means that they are considered together, as a single unit — as shown by the bracketed sentence above.

If the sentence had been something like "The clock is blue and driven by a motor" then the motor would have nothing to do with blue because blue and driven are different.

To separate rigged from driven by greed, simply remove the and. You do need to introduce semi-colons, though, because it's essentially a list of what cynics tell you. Making it a list also allows commas within the list items.

Cynics will tell you that everyone is selfish and weak; that the system is rigged, driven by greed; that you can never succeed, so it's pointless and contemptible to try; that all ideals are ridiculous, and the do-gooders are only out to show off their own supposed virtues.

The last comma might be a semi-colon, but in that case you would need "...ridiculous; and that the do-gooders..." because the that is being repeated in each list item.