My last 5 years returns actually do contain private information and SSN numbers, salary, sources of income, etc. The ATF form 4 does not. But I'll play. Your DL can be utilized to forward an identity theft, and form 4 really can't. So which one should you be more protective of?
If it's none of their business, then it doesn't matter what type of info is on there.
None of their business with sensitive information is none of their business.
None of their business with non-sensitive information is none of their business.