Because questions like that help flesh out positions.
It seems you mostly avoid them because you become concerned they put your position on rocky ground.
Take Johnson example. Your point is to say he isn't racist cause of legislation. Even though the way he spoke was obviously racist even for the time.
So I ask you a question about if racists passing anti racist legislation.
The answer is yes....we both know it ...but you don't answer because you know it's being attributed to Johnson and you don't like that shit.
So,you purposely reframe it,redirect it, and don't answer it.
To make it worse you then claim you did when everyone can clearly see you didn't.
It's why debating you never feels honest. It's like a point system instead of a conversation.