Point 1: For the government to require that all adult content be on .xxx, it would have to prohibit adult content on all other TLDs. That’s not constitutionally permissisible. Even if it were, what would the government do about non-US citizens who own and operate .com adult sites outside the US? What about .uk adult sites? As a practical matter, it’s not possible to effectively segregate content in this way. Moreover, if the government is trying to outlaw dirty pictures, we’ve got bigger problems than whether the dirty pictures are at .com or .xxx.

Point 2: If it’s voluntary, which it will be, this is a non-issue. If it’s not voluntary, see point 1 above.

Point 3: Who cares? This is for the .xxx people to worry about. If no one registers the domains, they’ll go out of business. That’s not a reason to prevent them from doing it.

Point 4: This isn’t even a point, it’s just your speculation. Given the number of major adult companies that support the .xxx concept, it’s probably wrong.

Point 5: No one is compelled to register .xxx domain names. If trademark owners choose to register .xxx domains defensively, that’s their choice. If they choose not to, they can still sue anyone who infringes their trademarks.

Also, this concern is not unique to .xxx, it’s an issue with all new TLDs. The .xxx people shouldn’t be expected to have a perfect solution, since no one else has.

Conclusion: Everyone presumably agrees that it would be nice if there were a way to keep Internet porn away from kids. .xxx might help achieve that goal, or it might not. The fact that it might not work isn’t a good reason to prevent its proponents from trying it, since there’s no apparent downside.

Those who disagree with the last statement should consider: if the government wants to segregate porn, why couldn’t it just do so, whether or not .xxx exists? How does .xxx make any difference?