a religious organization should pay taxes like any other.
With their contacts with Hollywood accountants, Scientology would probably have a better chance than most, of somehow retaining its nonprofit status in spite of your suggestion. "That wasn't a dividend! It was an expense!" You could end up with a situation where most churches have their profits taxed but Scientology's profits would still be untaxed.
(Though now I'm having a little smirk here, thinking of government auditors auditing Scientologist auditors. "Tell me your secrets." "No, you tell yours!")
Ok, so you (hey, me too) would probably see that as an improvement over the status quo, even if it failed to address this particular Enemy of the Day. But are we representative of American voters? I don't think that would work out for whatever politician enacted the change. I think most voters would be angry, because they're still very mystical, yet only a relatively small fraction happen to shop Scientologist.
The answer to crazy spending isn't to tax it; the answer is to reduce that spending (e.g. persuade their customers to spend on something else instead). Target the gross revenue, not the profits, and you'll still end up hitting the profits too.