Why do people get so upset when someone blocks them?

Obviously you are a very confident and secure individual who doesn't need the approval or even the acceptance of those people who may block you. You have the innate ability to accept reality - whatever that reality may be, but there are others whose personal lives are so negatively influenced that blocking is just another way of stamping the label "Rejected" on their backs. It is painful for these people but they don't know how to handle their feelings in a mature manner; therefore, they choose to react with anger. Don't let this bother you too much because you can neither change them nor help them. The ball is completely in their court and what they do with it is strictly up to these people - individually and as a whole.