He is missquoting that rule.
Fact of the matter is, the rule he is talking about applies specifically to the "spend defense tokens" step of the attack resolution stack.
in other words, the spending of the token to trigger a card effect would have to happen when defending from an attack. You can't just decide to discard a token at your convenience!
Not true, I am relying on this rule:
“[d]efense tokens can be spent as part of a cost for upgrade card effects. If spent in this way, a defense token does not produce its normal effect.”
It allows you to spend defense tokens outside of the "spend defense tokens" step of the attack resolution stack.
Otherwise, you could not spend defense tokens for Turbolaser Reroute Circuits or Vader.
The bottom line is as long as there is a "cost" associated with an upgrade card, you can always spend defense tokens to trigger that effect at the appropriate time.
Here, the questions is if the spending of a defense token qualifies as a "cost" for the purposes of devastator. In a literal sense, yes, there is a "cost" associated with triggering Devastator (you have the cost of not having those defense tokens for the rest of the game), you can't argue against that. The issue here is if the "cost" that the aforementioned rule is talking about ONLY applies to situations where a card says "spend X get Y." The rules are not explicitly clear on that and that is all I am pointing out.
Edited by mortetvie