If you say you want insider stock trading to be legal as long as you wear a suit, but your rationale is "it's so easy to convict innocent people of insider stock trading that the benefits from stopping false convictions outweighs the harm done by the insider trading", then that's the noncentral fallacy--a noncentral use of "want". Normally saying that someone wants X carries the connotation that they like X and don't believe X causes harm, which isn't true in this case.

If you don't want people to be convicted of rape based on evidence obtained by torture, you also "want rape to be legal" (specifically, you want the subset of rapes "rapes where evidence is only obtained by using torture" to be legal) but describing it that way would be misleading. You don't think rape is good, you just think encouraging torture is worse than rape. It would be possible to think that encouraging false accusations is worse than rape as well (especially if false accusations are common) and want to allow some rapes so you can discourage false accusations in the same way that you might want to allow some rapes to discourage torture.

(I really hope it's okay to even talk about this. I would rather not get banned.)