While this might not be as helpful as you'd like, I volunteered as a non-brony to watch the episode voted on in this old thread
I watched "Sonic Rainbow", which was the episode the most people wanted me to watch. My response:
Alright, I'm back after watching "Rainbow Dash"...
and I still don't get what the big deal is. The episode itself wasn't terribly funny (though moments did make me smile). The story was terribly predicable. Lastly, I don't think there's ever been a character that I wanted to punch then the one with those butterfly wings.
Granted, I recognize it's a kids show but when MLP fans are making it sound like the second coming of Christ and He brought everyone a magic box that never runs out of Krispy Kreams that don't affect your waistline, it's going to disappoint.
I'm not exactly the target audience but there are plenty of "kids" shows I love. Animaniacs and Powerpuff girls (PPG certainly being a "girly" cartoon) were two I loved growing up. Today, Fairly Odd Parents is one I find chuckle worthy but this just wasn't doing it. Great if you like it and I can feel alright critiquing it now that I've given an episode a shot.
Lesson of the story? If you're just trying to force the show down their throats, it's not going to work...at all. From your OP, it looks like you've had to bug them a lot to get them to try it, which means they are going in with the viewpoint of "This is stupid" already. I'm sorry that I have to be the one to break this to you MLP fans: The show is not good enough to change someone's opinion if they're going in thinking it's dumb.
If they want to watch the show, go for it; maybe they'll like it but if they're going to watch it just to "Prove how dumb it is", the show is not good enough to win them over.
While I agree with you, please take your argument with this asshole to PM so as to not derail the thread?
Also, that's not showing the power of friendship very well, now is it?