Mickyman... that is a somewhat unfair allegation. Easyjet, to their credit, have successfully built up routes on their own merit. LPL-AMS, BRS-BCN, NCL-CIA to name but a few. They operate out of regional airports offering flights to destinations that those airports could only dream about. They have made flying more accessible and affordable. In other words, on many routes, they have increased volume.
On key routes such as LON-CDG, as a relatively new airline, they were always going to be the "newcomer" on such routes but their very presence has made fares much more competitive. Furthermore, it makes good business sense to exploit busy/lucrative markets....it's business. With that in mind whilst I do believe that MAN should have and could sustain SXF, MAD etc a business will go where the most money can be made. Easyjet does not have an obligation to ensure MAN has a flawless route network. That is the airports problem so to speak.
As an MAN enthusiast, I too want MAD and SXF etc to return to our departure boards and think it is a dying shame that they disappeared in the first place. However you also have to look at it from oure business logic. That said, I am confident that eventually these destinations will return, very possibly courtesy of U2, if not another carrier.