It's not taboo because you are not taking it seriously. Now, would a newspaper let me write this? Would my family treat me the same if I were serious with this opinion?
Maybe I don't have a good grasp of the cultural context, but it seems to me that you would be much better off tweeting "I believe that capital punishment should be used for even minor crimes" than something like "I think it's okay to own black people".
Hell, I spent a full thirty seconds wondering whether I should even post the latter under my name, even if it's clearly in a hypothetical context and I'm just mentioning it as an example.
This one isn't. Here, I can say "there should be capital punishment for every minor fault!" and nobody will bat an eyelid. Nobody will agree, which is why it's okay to say this.
"Taboo" means "opinions you can't talk about", not "opinions that won't be popular". Many taboo opinions are extremely popular, such as "homosexuality shouldn't be a crime" a few decades ago.