All the chewy goodness of fallacious reasoning in new fun-sized bites!
The phrase “red herring” comes from the method of distracting hunting dogs from their original scent.
A red herring, according to John Nolt et al., is “an extraneous or tangential matter used purely to divert attention away from the issue posed by the argument.” In other words it is an irrelevant rhetorical device (masquerading as relevant) often used to evade the real issue.
Its logical form looks like this:
1. A claim is made
2. A second claim is made
3. The first claim is abandoned
Anselm’s notion of God as a maximally great being has merit but there are lots of ways that the word “God” can be interpreted. So it’s best not to be dogmatic when it comes to these things.
Since the second claim, that there are lots of ways that the word “God” can be interpreted, has nothing to do with the first claim, that Anselm’s notion has merit, then it is irrelevant to the original issue. In order to avoid this fallacy, always assess whether or not someone’s (including your own) consecutive statements logically follow.
The best way to point out someone’s fallacy is by using the Columbo tactic as laid out in the Funsized Tactics series. There are plenty of excellent resources available in book, e-book, or PDF format. Two good places to start, with regard to formal and informal fallacies, are A Preface to Philosophy by Mark B. Woodhouse and Schaum’s Outlines: Logic by John Nolt, Dennis Rohatyn, and Achille Varzi.
 John Nolt, Dennis Rohatyn, and Achille Varzi, Schaum’s Outlines: Logic, 2nd ed. (New York: The McGraw-Hill Companies, 2011), 204.