Only diff is Bill seems to really hate Welker; which is confusing because of all the people who've left and Bill has been seemingly okay with, Welker's departure shouldn't have been that bad.
Welker: Played hard here, never complained (in public), never held out for more money. Thought he was worth a lot more, only wanted to play for a contender, realized he wasn't, asked the Pats to match the Broncos seemingly similar offer. Patriots respond that they've moved on (day 1 of free agency). Result: Bill hates Welker.
Moss: Was seemingly great character for 3 years. Then went mental in he fourth year, and was essentially given away. Result: Bill talks about Moss like he's the world's greatest person
Branch: Holds out for more money, has to be traded away. Result: Bill welcomes him back
Mankins: Holds out for more money AND badmouths the ownership. Result: He gets his contract. Likewise with Seymour except less badmouthing
Honestly, I really can figure out why Welker is hated given all the other players that have left under worse conditions and still get Bill's respect. Maybe Bill and Rex are best friends and Bill holds Welker's comments against him.