«إذا ما تميمي أتاك مفاخراً»
If a man of Tamīm comes boasting to you.
«فقل عد عن ذا كيف أكلك للضب»
Then say: leave that aside—how do you eat the lizard?
The speaker does not answer the boast by debating ancestry directly. A seemingly comic question about food undercuts the boast. The humor is the form, while the serious intention is disparagement of the display of pride.
This is a rhetorical example of social satire, not adequate evidence for general claims about the actual customs of an entire people.