Also Bonus: There is absolutely no way to tell how an individual will react to the poison, some people have allergic reactions that make it even worse, some people will feel relatively few effects. So not only was Walt making a huge gamble with an extremely dangerous poison (which the show suggests almost DID kill Brock - thus the relief on Walt's face at the end), but he did it only to save his own ass. Instead of taking responsibility for his actions, he poisoned an innocent child.
Man he did so many reprehensible things this episode it was delectable. It almost makes the absurd Gus shot worth it so we could once and for all put aside the debate about Walt's sympathetic nature. Now we know people who think he is sympathetic are insane and can laugh about it amongst ourselves with little to no possible recourse.