European countries have a concept of "moral rights" along with copyright; one of the moral rights is the author's right to preserve the integrity of his or her work.
American law has always rejected this concept of moral rights. When the Senate ratified the Berne Convention, they did so with the understanding that acceding to the Convention would not sneak moral rights into American copyright law. Copyright is to "promote the progress of science and the useful arts", and forbidding ClearPlay (or the other kinds of editing you mention in your post) would not do anything to promote such progress.
If the filter is useless without a separate copy of the DVD (or other work) being filtered, then I think it qualifies as fair use, even if the filter is being sold for a profit, because everyone who buys the filter also buys (or rents) the work being filtered, and therefore the owners of the original work's copyright are not seeing their profits reduced.
(One could argue that the owners of the original work might want to make their own sanitized version and sell it at an even higher profit margin, but with the filter, this option for making more money is closed off. I think that argument is a big stretch, though.)
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American law has always rejected this concept of moral rights. When the Senate ratified the Berne Convention, they did so with the understanding that acceding to the Convention would not sneak moral rights into American copyright law. Copyright is to "promote the progress of science and the useful arts", and forbidding ClearPlay (or the other kinds of editing you mention in your post) would not do anything to promote such progress.
If the filter is useless without a separate copy of the DVD (or other work) being filtered, then I think it qualifies as fair use, even if the filter is being sold for a profit, because everyone who buys the filter also buys (or rents) the work being filtered, and therefore the owners of the original work's copyright are not seeing their profits reduced.
(One could argue that the owners of the original work might want to make their own sanitized version and sell it at an even higher profit margin, but with the filter, this option for making more money is closed off. I think that argument is a big stretch, though.)