I have proposed a solution to this: have the snippet self-hashed and verify with multiple sources. eg:

A=$(curl -L https://get.rvm.io);echo "$A" | shasum -a 256 | grep -q 05b6b5f164d4df5aa593f9f925806fc1f48c4517daeeb5da66ee49e8562069e1 && (echo "$A")