Mountain Biker to appeal Olympic non-selection

Generally we as a society are so fixated with winning or the final medal count. At what point does the Olympic ethos (that the Olympics 'prides' itself on) slip below the commercial success or wider appeal of an event like this?

Should all top athletes be allowed to compete at the games (provided they aren't on any performing enhancing drug charges etc. or serving a sentence) to ensure that the 'best of the best' were present?
Does it mean that any top athlete involved in a physical altercation (outside of the sporting arena) automatically be banned?
Do all countries employ the same selection criteria?

I suppose one needs to define sportsmanship and what it means to be an athlete in this day and age.

PS - Is it just me or is it odd that an athlete can represent his/her country at the world champs but is not allowed to partake in the Olympics?