Why would serious cyclists want more people to get on bikes?
Well, I think in this case you can compare the cycling community (in some places) to the Ruby community. They want everyone to ride fixies (or whatever the trend du jour would be), and if you dare suggest that your needs are better satisfied by some other solution, they will tear you apart with great enthusiasm.
Of course, they could just be dicks and say they don't care if other people start cycling. In which case, they don't get to wear helmet stickers touting their "zero emissions vehicle" or complain about SUV drivers.
Either they need to be more friendly about getting more people on bikes or stop sneering at people who don't have them. They can't have it both ways.