I strongly disagree with that statement because I've learned to be be suspicious of "all or nothing" dogmatism whether it exists in religion, politics, or programming.

Source filters are unsafe. Very unsafe. They are not, however, evil. Ignoring the moral implications of your words (because I don't think that's what you meant), source filters can provide a way of significantly easing some coding burdens for features a language does not inherently provide. They can be extremely dangerous when you're trying to do things that are too complicated (such as using them with Perl :), but if you put in the extra time and effort to do one right, the payoff can be huge though one must be cognizant of the inherent risk. The risk/reward ratio is what one must consider here. Not all or nothing dogmatism.