I sympathize with the alleged prejudiced housing policies, if they are in fact true. I don't get the outrage about tweets. The tweets that got re-tweeted weren't racist in the least, is the guy or gal in charge of his Twitter account (I assume it's not him, i'll give you that) supposed to look at the history of every tweeter to see if tweets they come across are from racists? If anything, one of the staffers doing the retweet screwed up and didn't vet the messenger, but that's hardly a blemish on Trump other than "lesson learned, vet your tweets better."
Edit: Some of the tweets he's re-tweeted are pretty questionable, i'll give you that much. I only saw a couple before, one about Jeb Bush which one article had as it's prime example so I was pretty confused.