I usually try to stay away from these kind of threads, but I couldn't help myself.
I've been kicked several times from an LFR run for absolutely no reason. Best one I remember was tier 13 LFR part2 (ultraxion-MoD). Wanted to help a few guildies' alts and joined their group, waited my time in the queue and a minute into the ultraxion trash I got kicked. I said nothing and was dpsing the dragons, even pulling them down since I play a hunter and I could use distracting shot to "taunt" them down. My guildies told me on vent the reason was my gear, apparently.
I wasn't really excluded from content since I had done it before (and continued to do a weekly guild run) but I was still excluded from that particular LFR group for no good reason. Whether it's "the casuals" or not, some people definitely didn't want me in their group and enough people agreed so I got kicked. The others times this has happened I doubt it was my gear causing it, since I've been a casual in MoP and LFR offers upgrades to me. But some things haven't changed; every LFR I join I do my best to make it a fast, easy clear and stay quiet, unless I'm being spoken to directly.
I guess my point is, there are idiots on both sides. Always has and always will be, and there's nothing you can do to stop it. Best you can do is ignore them and try to enjoy the rest of it.
If you check my armory (link in signature), hover the dragon soul LFR statistics - all of those kills are in full guild groups done within the first 2 weeks of the patch (part 2 wasn't open the first week).