On the one hand: health insurance premiums are entirely deductible if you have schedule C income that exceeds their value. This covers more or less all self-employed people, who are the largest group paying for their own insurance.
On the other hand: health insurance premiums are not deductible if you do not have schedule C income that exceeds their value (and/or are eligible for an employer subsidized insurance policy), which means there is still a sizable and significant group of people paying for their own insurance and not able to deduct it.
I am sure you know my own preferred answer: convert all health insurance premiums into taxes that fund a single payer system, so that there is no difference between self-employed "self payers" and non-self-employed "self payers".
Given that we're unlikely to see that before I'm pushing up daisies, I would agree that either any health insurance premium paid by the insured should be tax deductible or none of it should be, to level the playing field. I think I slightly prefer the none solution, but I'm not actively against the all version.