I don't use the stock mail app all that often, but I cannot think of a setting that does what you want. Of course, I prefer including context in my replies. I disagree with you; I think that it's unprofessional to reply to a message without including at least part of the messages that you are replying to. People don't always recall what they've sent when they read your replies. Back "in the day", people with AOL accounts always replied without context, which I assume was a default setting for AOL, and I sometimes had to look back at what I set to get some context on what they were talking about. However, I digress.
Anyway, one trick: in the original message, highlight a single word of the message, by long-pressing on one of the words, then hit reply. The only part of the original message that will be included in the reply is the single word, which can be more easily deleted from the text of the reply.
Of course you can also long-press in the replay before you type and "select all" and "cut" to remove all of the text before you compose the reply.