Nowadays when I think about womens underwear I can't help but think of it as a conspiracy. For some horrible reason, whenever I used to wear them I would get horrible, horrible wedgies ALL of the time! 'Boy' shorts were the WORST! Boxerbriefs and boxers were marginally better, briefs an improvement on that, but recently I've discovered the JOCKSTRAP. When I wear them, I never get wedgies, EVER, because... Well, since there's no fabric covering your ass, there's no fabric going UP it. I also supports my prosthetic really well, so I don't have to worry about it flying around in my pants/ending up sideways when it isn't glued on.
As for advice, I remember my dad acting kinda funny when I asked him about boxers when I was in my teens, too. I'd just tell them it's for sleeping purposes- I mean, especially if you have friends over or go to friends houses, explain to them that you don't need anyone seeing you in panties under that circumstance. I've known girls, even, who wear panties and put boxers on TOP of them during sleep overs, for modesty. Boxers are more acceptable to wander around the house in when it's hot- I imagine parents could empathize with that, as most of the ones I've met would rather not see their kid running around the house in panties! Too revealing!