To be honest i like it but i prefer it further down the race on initial climbs or on straights where there arent that many fans.
Its not that great when they are on the more crowded bits of the mountain and get into riders faces.
Didi and that antler dude with the flag get it. They do it 60 k from the end often, when there isnt that much going on and often the riders are in the mood for a bit of fun.
Thats why Flecha took antler guys flag and everyone laughed. It was a while from the end, the riders were in the mood to have a nice distraction.
They also appreciate the fans at that stage.
Do it when the riders are riding into the red, emotions very high and its annoying.
That way the fan also gets a lot more tv time too.