Bigotry

Is there a fallacy in where one claims that the only reason one is arguing for x is so that they can simply justify their bigotry, and therefore the claims one makes are invalid? 

Yes, the scenario you described involves a specific logical fallacy known as the "Ad Hominem" fallacy. An ad hominem attack is when someone criticizes or attacks the person making an argument rather than addressing the substance of the argument itself. In this case, dismissing a person's argument by attributing it solely to their supposed bigotry is an example of attacking the speaker rather than engaging with their claims or evidence.

This type of reasoning also risks falling into the trap of "Motive Fallacy," where the motivation behind someone's argument is used to invalidate the argument itself. While understanding someone's motivations can provide context, it does not inherently invalidate the argument they are making. Each claim should be evaluated on its own merits, using evidence and sound reasoning.

It's essential to separate the argument from the person making it to avoid these logical missteps. Sound reasoning involves critically assessing the evidence and logic presented, regardless of any perceived biases or motivations of the individual presenting them.