Purples haven't meant anything since Wrath, so don't get so caught up on that thing. Keep in mind, that while an LFR player may have all their purples from SoO and you're only halfway through gearing SoO normal with the rest ToT Normal, you STILL have better gear than them over all. As far as giving them no motive, if they want to experience the harder raiding, there's nothing necessarily stopping them from doing so. If LFR didn't exist, they just wouldn't raid. LFR existing means more players have a reason to continue paying $15 a month to play, and business wise that's a good thing. Heck, community-wise that's a good thing. I know three guildies who have fallen in love with Raiding because of LFR, when before they thought it a waste of time. They are some of our best DPSers (and one tank) in our Normal runs now.