It's a double standard for a reason. Teen boys are horny as fuck and starved for pussy. A hot female teacher fucking him is doing him a solid. If that happened to me I would be fucking ecstatic.
It's still wrong obviously, but it's not the same as the other examples that you cited.
It's like someone stealing your wallet but returning it to you with an extra thousand dollars in it. Sure, they committed a crime by stealing your wallet, but are you really mad about it in the end?
The problem with such hypotheticals is that they assume perfect equivalency between scenarios. In most cases this might be technically correct, but would not necessarily feel the same morally. Argumentative people these days worry too much about being consistent in their argumentation, rather than acknowledging that their argument is built up of unproven extrapolations., making the outcome dubious at best.
OT: Technically it is illegal to have sex with a student, so teachers should not do it. But societal response shows that, trite philosophical arguments notwithstanding, there is a difference in how these cases are perceived, and so it is not unwarranted to ask that they be judged differently as well.
