Instead of asking Moshe to answer the angels and then having to shield him from harm, why didn’t G-d just answer the angels himself? After all, it was G-d’s choice to give the Torah to mankind just as much as our choice to receive it!
Maharal in his Derush al haTorah explains that we see from the gemara that Torah was given to mankind because man has imperfections. Torah is a roadmap to overcome faults and grow – something angels cannot do. But that process is possible only if one has self-awareness. Unless a person is cognizant of his own faults and shortcomings, he can never aspire to anything greater. Therefore, G-d could not answer the angels – the answer had to come from Moshe himself. Our own kabbalas haTorah as well needs to start with the self-awareness; with the knowledge that we are imperfect and need that roadmap to get somewhere better.