I wear lycra when riding my road racer but when on my tourer or MTB I usually wear my Endura shorts or Keela longs, but the Enduras have a lycra short inside.
I may be classed as a Mamil but when you have been wearing it since you were much younger ( with a wash though) then that's not a good term, especially if you've been riding all your life. It classes everyone of a certain age as a newbie wanna be.
I know the ones you mean, there is a person near to me who works off shore and took up riding last spring, passes me all the time in his team SKY gear, head to toe, on his Pinarello Dogma. You don't see him out much now its cold.
Personally I get more amusement from the mtb boys who have a snigger at my old steel 1X1 or Pugsly singlespeed while pushing a bicycle shaped object up a climb but riding the same trails down but dressed in every piece of body armour looking like a plastic stormtrooper.
On a personal note it doesn't really matter what you wear when riding as long as your riding, the examples mentioned above are a couple of amusing individuals but I would rather they were riding their bikes than not. I'm not the bicycle police and so what it means to me is maybe not what it means to anyone else. That's what I like about it, its always peronal, whether racing mtb or riding the road, touring etc.
Jamie