VioletSky
People don't have sex at Pride?
I don't know Violet - do they? 
PRIDE is about diversity. I'm sure in everyday life those taking part do very ordinary things like shopping, working, cooking, cleaning, etc - but that is not what they are celebrating is it? The whole point of PRIDE is for those on the marches, events, to claim pride in who they are, legitimately.
When grandad - or indeed, grandma, or in fact anyone - strides out in their fetish, bondage, whatever, apparel, they are emphasising (celebrating) their sexuality, as they are when they wear an item of clothing that accentuates a particular body part. It's about sex as much as it about everything else.
Of course, they don't all dress that way - some just wear ordinary clothes - but that illustration of grandad in his 'gear' is exhibiting his sexuality... so explain that to a four year old.