The reason why McDonald screwed up its Twitter campaign is because it did not have a good Twitter strategy to counter these vile unhappy McDonald's eaters. What they can do was to make sure that its good news Twitters message go out only to those who are happy to hear it, meaning its happy fans, not some losers who are looking for an excuse to lent out their frustration in life. So, yes, maybe customers must be treated equally, true, but in term of customer relationship that nurtured good customer relationship with your good customers, well, you have to draw a boundary, it is your site, so politely remove those vile comment makers, there are those various Tweeter tools available after all, and just give out your messages to your happy customer base, which in case of McDonald's, huge. But, you can keep track of those unhappy customers too, and see what sort of comments they make in other Tweeter sites they go. Those trouble makers themselves are interesting people to research for McDonald's (like, how to counter their vile comments, or to see if there is anything valuable you can salvage from their opinions), but, they are not to be invited to your customer relationship sites.