I don't think this is even remotely true. Try going down to a city park and getting into a pick up basketball game. Now try it out of shape and wearing penny loafers and see how many times they pass you the ball. Isn't this similar to what the OP did?
Ever just walk up to a bunch of soccer players getting ready to start a game and see if you could join them? Maybe hop into a volleyball game or a softball game? Would you usually be welcome? Cycling is one of the only sports where a complete outsider is welcome on most rides. Yes, there are a few "elitists", but there are far more friendly and welcoming bike riders and racers.
That sounds about right... A strong rider will be able to keep up with the group and not cause problems, regardless of the equipment. But more often than not, the equipment is indicative of the rider. If someone shows up to the local hammerfest on the OP's bike I would be skeptical, I may even give them a funny look. If I still see them later when we are going 30+ I will have a completely different opinion of them.
And regarding the self-preservation, that's a very strong factor. I drifted a little bit on Saturday and bumped into a rider coming up behind me on my left on a descent. I wobbled a bit but didn't go down, and he yelled at me to hold my line. He gave me looks and a wide line the rest of the ride, and he knew me. I don't know why anyone would come into a situation as an unknown quantity with equipment that screams inexperienced and expect people to not have some hesitation of your abilities.