[DanaC]

First, it was made-up by a bunch of business speakers trying to have their own business/motivational speak that ended-up escaping their little world.

You just described how a great many words have entered our language over the centuries. Specific interest groups have always come up with their own vocabularies and it has often leaked into the world around them.

Language is a changing, fluid thing. It isn't set in stone. The word proactive, has been around for over half a century. Much about our language has changed in that time.

Secondly it is a double-positive, making it meaningless.

Not really. The 'pro' part refers to the sequence not to the act intself. It s the use of action to forestall something, not just a very positive version of 'active'.