As usual, the penetrating question of the students is one that has been addressed in the past. Over the centuries many answers have been suggested. I related some of the answers that I have heard in past years.
Unlike the Bnei Yisrael, Yitro did not witness the miracles of Egypt and the red sea first hand. The Torah makes a point to say that Yitro heard about what happened. There is an aphorism found in the Gemara that says hearing is not the same as seeing. One of my congregants is in sales and he told me that he lives by this principle. When giving a sales presentation his mantra is always, "don't tell it to them, show it to them!"
For the Bnei Yisrael to accept the Torah was a no-brainer. They had witnessed first hand the greatness of Hashem as he personally came to rescue them from slavery. The giving of the Torah at Sinai was an offer that they could not refuse.
But Ytro was different. He did not see the plagues in Egypt, he did not see the splitting of the sea, and God did not personally come down and do anything for him. In a sense, he was an unbiased and objective consumer. Yitro was drawn to the Torah because he believed that the Torah represented truth. He was sold purely on the strength of the Torah's ideas.
Yitro is brought into this parsha of the accepting of the Torah to teach this important lesson. There is a place in Torah education for emotion, nostalgia, and feelings of loyalty towards tradition, but if that is the extent of the education then none of those feelings will ultimately endure. The strength of our tradition lies in the truth of its ideas.
At Har Sinai our ancestors had no choice but to accept the Torah. We need to be like Yitro. We need to explore the Torah and come to love it for its essence through learning, questioning, and sincerely seeking for answers and truth. That is how we can accept the Torah.