Emulation allows them to relive their youth, reminding them of why they started playing games in the first place and refiring enthusiasms perhaps rather dimmed by today's endless diet of racing, fighting and Command And Conquer clones. Start throwing IDSA's massive weight at these people in such an unfriendly way and you might just lose them - for absolutely certain, you're definitely not going to make them MORE likely to buy more games. Emulation costs you, the members of IDSA, nothing. Older games aren't for sale anywhere any more, no-one was making any money out of them. And let's face it, anyone determined enough to be a pirate that they spent three times the cost of their console on a copying device isn't going to be dissuaded by you driving emulator sites underground.
Emulation sparks interest in modern games.
Someone who's played, say, the first six Final Fantasy games on emulators, is only going to be MORE likely to go out and buy FF VII on Playstation, not less. Emulation is nothing more than free advertising, and the most effective kind of free advertising at that. Absolutely no-one is trying to say that there's no copyright on all these old games any more. People aren't stupid, they know the difference. Of course not.