I was a kid back then, too. Although I knew to keep my attraction to men a secret, even at age four, it was easier in some ways, because even when people saw indications, their minds didn't always go right there.
For example, in the early sixties, the YMCA in Buffalo, New York, was still requiring swimmers to be naked in the pool, on the grounds that the filter couldn't handle the fibers shed by the woolen swimsuits still common back then. Naturally, the sexes were segregated, but none of us guys were embarrassed to be naked in front of one another (and I presume the same went for the women).
These days, it seems the increased awareness of gay people has, ironically, worked to make people more uncomfortable with exposing themselves in front of others of the same sex. That's why Dan's entirely reasonable attitude seems so striking, lol!