by Ender02
Direct from the rulebook about removing spic and poison tokens;...You can't get rid of these counters whilst you are in Tokyo, because it must be instead of healing.
So since you can't heal in Tokyo, you cant us an action that would be done in place of healing because you can't heal in the first place.
To answer the OP's original question, the reason you can't do it is because the rules directly say that you cannot. Pretty much end of argument.