Because scoring can be subjective, these sports all have a built-in protection against bias: The low and high scores in each event are discarded, leaving the remaining scores to be averaged, combined or otherwise calculated in some (usually highly technical) way.
If you ask your audience to fill out evaluations or give any kind of feedback after your presentations, you will also discover bias among your "judges."
Some audience members will love you to pieces no matter what you say or do. Some will just not click with you, no matter what you say or do. The rest will be along a continuum somewhere in the middle.
As I wrote in this blog post, paraphrasing Scott Ginsberg, it's far too easy to dwell on the 10% who have negative things to say, rather than the 90% who are more positive. But the truth is, there will always be that top and bottom 10%, who are both probably equally unreliable indicators of the overall quality of your presentation.
When analyzing your evaluations, or even if you're just analyzing your audience's reactions in the moment, remember to discard the highest and the lowest "scores," and you'll have a more accurate reading of how your audience is truly responding to your presentation.