If science proves facts that conflict with Buddhist understanding, Buddhism must change accordingly. We should always adopt a view that accords with the facts.
There has to be evil so that good can prove its purity above it. To live a pure unselfish life, one must count nothing as one's own in the midst of abundance.
The Buddhist tenet, "Non-killing is supreme virtue", is very good, but in trying to enforce it upon all by legislation without paying any heed to the capacities of the people at large, Buddhism has brought ruin upon India.
Here's an example: someone says, "Master, please hand me the knife," and he hands them the knife, blade first. "Please give me the other end," he says. And the master replies, "What would you do with the other end?" This is answering an everyday matter in terms of the metaphysical. When the question is, "Master, what is the fundamental principle of Buddhism?" Then he replies, "There is enough breeze in this fan to keep me cool." That is answering the metaphysical in terms of the everyday, and that is, more or less, the principle zen works on. The mundane and the sacred are one and the same.
Modern Hinduism, modern Jainism, and Buddhism branched off at the same time. For some period, each seemed to have wanted to outdo the others in grotesqueness and humbuggism.