The meaning of the abstract noun gratitude can be expressed with the phrase "give thanks." It can be made explicit that the thanksgiving is to God. Alternate translation: "If I give thanks to God for the food when I share in the meal" (See: rc://en/ta/man/translate/figs-abstractnouns and rc://en/ta/man/translate/figs-explicit)
This is a rhetorical question, and it can be expressed as a statement. The verb "be insulted" can be translated with an active form. Alternate translation: "I should not be insulted for that for which I gave thanks." or "People should not be insult me for eating food that I have thanked God for." (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-activepassive]] )