Disputing what is considered to be fallacious

I have come across some arguments which are in favor of Natural Law, in which the reference to homosexuality being immoral is mentioned. I have also come across an objection to the Ad Hominem fallacy, one in particular stating that if a man (or woman) made 100 idiotic remarks, that it would be silly for us to not chalk him or her up to be an idiot and call it a day. Ultimately, my question is, who determines what is or isn't fallacious, and can what is currently seen as being fallacious be disputed? As a bonus question, is there some sort of standard we appeal to when determining something to be fallacious?

Hi Marko. I go over this answer in detail at logicallyfallacious.com. Some more thoughts based on your question:

If homosexuality exists in nature, then we can call it "Natural Law" or simply say it is "natural." This is stating a fact, not making an argument, so no fallacy. However, if we say that because it exists in nature, then it must be right, we are committing the fallacy.

If a person is consistently making idiotic remarks, then we can call them an idiot. No fallacy, just an opinion being stated. However, if the idiot argues for X, and we claim that X is wrong because the person is an idiot, then we are committing the Ad Hominem fallacy.

Some fallacies are objectively (certainly) fallacies (e.g., the formal fallacies dealing with form) but most are subjective and can be argued. Some are more fallacious than others, just like some men are more bald than other men. There is no generally agreed upon criteria for fallacies, so that is why I have my own that I believe makes the most sense (out of all I have read) and I would be willing to argue for the validity of this criteria:

Dr. Bo's Criteria for Logical Fallacies:

1. It must be an error in reasoning not a factual error.
2. It must be commonly applied to an argument either in the form of the argument or in the interpretation of the argument.
3. It must be deceptive in that it often fools the average adult.

Therefore, we will define a logical fallacy as a concept within argumentation that commonly leads to an error in reasoning due to the deceptive nature of its presentation. Logical fallacies can comprise fallacious arguments that contain one or more non-factual errors in their form or deceptive arguments that often lead to fallacious reasoning in their evaluation.