Well, violence was the norm for most of human history, too :-) Violence is as much a part of the human psyche as sexuality.
If you start human history from, say, 2 million years ago (or even about 100K years ago, which is the assumed date for the rise of language), yes you're right. However, by the time of Greeks at last, who were big proponents of nudity (men only, of course), this behavior was not the norm, in Greek sources it is often mentioned that other nations express shock at them for their cavalier attitude.
If you start human history from, say, 2 million years ago (or even about 100K years ago, which is the assumed date for the rise of language), yes you're right. However, by the time of Greeks at last, who were big proponents of nudity (men only, of course), this behavior was not the norm, in Greek sources it is often mentioned that other nations express shock at them for their cavalier attitude.