Franklin's Gambit says that we often use data and explanations to justify a decision we've already reached, rather than actually prove that some choice is the best one.
This tendency is so innate to the human mind, our legal systems works to exclude it by design. The state collects it's evidence independently and then presents an argument in favor of prosecution. The defense collects their own evidence for an opposing argument. A judge presides over the trial, and a jury weighs the evidence and arguments before rendering a decision.
If a large IT organization is weighing the option of SQL Server versus Oracle, I think it would be near impossible for one individual to weigh all the options and make the decision without bias. The right way to do it would be for executive managment to announce that a decision will be made at some point in the future, and then play the role of jury, weighing evidence and arguments from various groups, perhaps even getting input from outside consultants as well.
"Do not seek to follow in the footsteps of the wise. Instead, seek what they sought." - Matsuo Basho