So far reasons given to him for behaving this way is theory as much as you can say he being fake is a theory also. Everyone have their own free will to make up their own minds.
I can have a theory that the shootings really took place in Japan, but that doesn't mean that it would be an equal theory in regards to the chances of it or in regards to the evidence for it.
Its already well understood in psychology and among a lot of the public that when people go through extremely tragic events that they can act in a variety of ways, many of which might seem irrational. "Irrational" behavior could be defined as someone acting in a mentally disturbed type of way. When someone has their child killed, a mental disturbance of some sort is exactly what we would expect.
Also keep in mind that when a tragedy like this happens, crisis response teams sweep in and make sure everyone effected has access to high doses of medication of the type that tries to increase "happy feelings" in the brain.
Making up one's mind in agreement with the alternative "theory", would imply somehow knowing for sure that a person who just had their kid killed cannot act in a certain way and just suppose to act like in the movies or whatever. When one make claims like this, don't be surprised if people ask questions or point out potential holes in it.