I believe Peter Singer actually originally advocated the asceticism you mention, but eventually moved towards "try to give 10% of your income", because people were actually willing to do that, and his goal was to actually help people, not uphold a particular abstract ideal.
An interesting implication, if this generalizes: "Don't advocate the moral beliefs you think people should follow. Advocate the moral beliefs which hearing you advocate them would actually cause other people to behave better."
Here's the new thread for posting quotes, with the usual rules: