"considered mad" is correct and usable in written English.
You can use it to describe someone who is widely recognized as being insane or mentally disturbed. For example, "The Beast of Gevaudan was considered mad by the whole village, so no one was willing to approach him."
Beane, especially, was considered mad for undertaking the project.
"In Poland," he said during a break from rehearsals, "I'd be considered mad and sent to a mental institution".
Tony Blair says he would have been considered mad to propose the kind of financial regulation now accepted as necessary.
In between came Cassavetes's "A Woman Under the Influence," in which Falk played a road-crew laborer whose wife (played by Cassavetes's wife, Gena Rowlands) is free-spirited and eccentric to the point of being considered mad.
There's a canny argument between Verwoerd's successors about whether the killer should be considered mad (in which case he couldn't be hanged) or politically motivated (bad PR for the regime).
There are always a few people in Hollywood who are considered mad dreamers for trying to do in movies things that have already been done in the other arts.
Until the discovery, Italy had been considered mad-cow-free.
And America wants to build a ballistic-missile defence, a project which most Europeans consider mad but which Britain feels it has to be polite about.
Considering Mad Men is a show that boldly explored all aspects of humanity, we shouldn't have been surprised that it was a series that ended on hope.
This is why he supported Thatcher after he believed she had gone off the rails and why he has backed Mr Cameron's misfiring policy of renegotiating Britain's place in Europe, which he must consider mad.
Some of our friends considered us mad for taking three children in a car on such a road trip with no electronic devices to distract them.
