You can disable smart quotes for your NSTextView with:
self.textView.automaticQuoteSubstitutionEnabled = NO;
Not setting the checkmark in the interface builder doesn’t seem to work since OS X 10.9 Mavericks.
See NSTextView setAutomaticQuoteSubstitutionEnabled:
Also you can use this for a more detailed control over the text replacement.
self.textView.enabledTextCheckingTypes = 0;
See NSTextView setEnabledTextCheckingTypes:
Also in Mavericks there is smart quotes enabled by default in System Preferences → Keyboard → Text. You can disable this as a personal preference.