Is it true that there is no absolute morality?

[bennyboy]

That would be moral opportunism.  The moral assessment, in that case, hinges upon the selective utility of a behavior rather than any moral fact of any matter.  

Yeah, the idea depends on the "existence" of a hypothetical best act, upon which an individual's attempts to act might sometimes stumble. In particular binary situations-- for example, kill someone or show mercy, you'd expect to have a 50% chance to get it right, but not to have knowledge yourself of whether you did. Thus the existence of alternative fiction novels where killing Hitler dooms the Earth, or saving Kennedy causes a revolution, etc.

It would get us closer to a maximally beneficial behavior.  

I'd define the maximally beneficial behavior as the perfect behavior.

No.  You may be able to say that Jims brain is objectively active in region X..you may be able to translate that activity into a verification of Jims firmly held opinion....but you are now talking about a brain..not ice cream, and whether or not chocolate is the best.   The latter remains a matter of opinion, even if the action in Jims brain is not.  The possession of an opinion, even if it is objectively verified as being possessed, as in your example...does not suggest or imply that the opinion itself is objective.

This is a very interesting situation, isn't it? Usually we are on opposite sides of this kind of discussion. I've enjoyed this thread for that reason-- playing Devil's Advocate is fun.