Bad design

I recently got into an impromptu debate with an atheist and evolutionist (i.e. a materialist or naturalist and neo-Darwinist). Well, calling it a debate might be too generous, since he didn't make arguments so much as assertions. One of the things he asserted was bad or suboptimal design demonstrates that intelligent design (ID) is bunk and that God doesn't exist. Or it demonstrates it's evil design from an evil designer.

My reply was along these lines:

1. As far as ID goes, the claim isn't that ID necessarily demonstrates God designed the entity (e.g. a biological organism). Rather ID makes a more modest claim: the inference is to design without necessarily identifying the designer(s).
2. Bad or suboptimal design could still be intelligent design. A Ford Pinto is just as intelligently designed as an Alfa Romeo despite the former cars being badly designed. A clunky and defective Gateway computer is just as intelligently designed as the world's best supercomputer despite the Gateway being a badly designed computer.
3. If (arguendo) bad or suboptimal design is somehow evidence of evil design, and by implication an evil designer designed it, it'd still be design. An iron maiden chamber, bamboo torture, and crucifixion might imply an evil mind designed these instruments of torture. Nevertheless there's an intelligence or mind behind them. ID doesn't make any certain claims about the moral values of the designer(s).
4. An argument from a design inference to the Christian God as the designer requires additional steps. These arguments exist. For example, Stephen Meyer's book The Return of the God Hypothesis argues for God as the designer.