Of course an opinion becomes an argument when we support it with arguments. The person making the argument has the burden of proof. A fallacy occurs when we violate the principles of good arguments. Including such things as relevance, emotion, linguistic confusion, unwarranted assumptions, lack of evidence, ineffective rebuttal, personal attacks, and diversion. Many fallacies have names some do not. The names are not important to understanding the fallacies simply useful identifiers. I'm going to present arguments that I find surfing the Internet, and see if I can discover why they are bad. I'll try to identify the fallacies and perhaps discuss ways they could be repaired or rehabilitated. I don't consider myself an expert, but am doing this to improve my own reasoning capabilities. Examples one finds in logic text books are often created just for the text because they are clear. Arguments you come across on the web as in life are seldom so simple. So jump right in if you think I'm off track I welcome your comments. I'm selfish, I wouldn't be doing this if I didn't expect to learn from it. I believe the real value in this exercise is to improve our own reasoning skills not in putting others down. So on to an example.

He has no problem calling people like me racists, even though he can't point to anything that I may have ever said that could even remotely be considered racist.

I believe this is a fallacy of division. The fallacy consists in assuming that what is true of some part is therefore true of the whole, it is also a problem with ambiguity. That's what I meant about real examples being more difficult than text book examples.

In this case the statement anything you said could be considered racist is not necessarily relevant [part], since the statement could still be true of the whole regardless of anything an individual said or didn't say. The problem is with the term "people like me" [this is the whole]. Since when someone uses the statement "people like me" they aren't arguing that they are identical in every way with every other person like them. Simply that they have some things in common. Now if the commonality they are referring to is that they all are not racist then you would be required to claim that every member of the group was not a racist and had not made racist statements not just one.

A related fallacy is that of composition. That fallacy consists in assuming that what is true of some part is also true of the whole.

It is important when making arguments that include groups and individual parts of those groups not to fall victim to fallacies of division or composition. It is also necessary to define important terms.