Majority of horse people I've met (whether professional riders, trainers, or pleasure trail riders) are nice, helpful and give you a hand when you need it. May be you just look at things in wrong way, or treat other people wrong so they give you some kind of attitude.
And BTW I never NEVER heard this stereotype from either horsey or non-horsey people. Frankly, I do find it to be offensive too.
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."