Obviously, in that instance he was speaking symbolically. When Christ spoke of baptism, He was actually getting baptized, so it is kind of hard to conclude he was speaking symbolically there.
Why even argue the point? If you are aware that you should be baptized but you do not, I am sure that will not score you many brownie points. People who are not aware or did not have the opportunity, will be judged on those facts.
"Obviously, in that instance he was speaking symbolically"
Disciples don't just walk away from symbolic speech! However, the point is that you disagree with others who feel sprinkling is sufficient/not sufficient for Baptism. Do you see my point? I agree with your last statement that one willingly refusing to join the Church (by Baptism) calls his eternal salvation into question.
Regards