In the comments, Conifold mentions ignoratio elenchi or red herring. Bo Bennett describes this fallacy as
Attempting to redirect the argument to another issue to which the person doing the redirecting can better respond. While it is similar to the avoiding the issue fallacy, the red herring is a deliberate diversion of attention with the intention of trying to abandon the original argument.
He also gives it various names:
(also known as: beside the point, misdirection [form of], changing the subject, false emphasis, the Chewbacca defense, irrelevant conclusion, irrelevant thesis, clouding the issue, ignorance of refutation)
However, he identifies avoiding the issue as a separate fallacy which may be closer to the OP's description of making an "irrelevant generalization":
When an arguer responds to an argument by not addressing the points of the argument. Unlike the strawman fallacy, avoiding the issue does not create an unrelated argument to divert attention, it simply avoids the argument.
Bennett also warns arguers about accusing an opponent of committing a fallacy. He views knowing about fallacies as valuable for self-defense and to strengthen one's own arguments. Besides accusing an opponent of committing a fallacy is an invitation for a counter accusation:
I caution you against correcting fallacies that your opponent might raise. As you will see in this book, fallacies go by many different names, and there are varying definitions for the fallacies. Except for a handful of fallacies that have been around since the time of Aristotle, most fallacies are under a continual redefining process that might change the name of the fallacy or the meaning of the fallacy. The bottom line is to focus on exactly what error in reasoning you are being accused of, and defend your reasoning—not a definition or name.
Bennett, B. "Avoiding the Issue" Retrieved on May 6, 2019 from Logically Fallacious at https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/61/Avoiding-the-Issue
Bennett, B. "Being a Smart-Ass" Retrieved on May 6, 2019 from Logically Fallacious at https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/207/Being-a-Smart-Ass
Bennett, B. "Red Herring" Retrieved on May 6, 2019 from Logically Fallacion at https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/150/Red-Herring