Final answer:
The words that best fit the blanks in the sentence are abrasive and condescending.
Step-by-step explanation:
The words that best fit the blanks in the sentence are abrasive and condescending.
When someone's comments are abrasive, it means that they are harsh and unkind. In this context, it means that the person's comments were unkind despite their smiling demeanor. Condescending means showing a feeling of superiority, and in this context, it means that the person came off as superior rather than charming.
Therefore, we can say that although he smiled when he spoke, his comments were abrasive, and he came off as condescending rather than charming.