Yes a sole proprietor can deduct disability insurance premiums from income for income tax purposes. If you choose to do this, it's important to keep in mind that the benefits paid by the policy if on claim will be received as taxable income and you will need to pay income taxes on the benefits received.
If instead you choose not to deduct the premiums, then the benefits can be received income tax free.
If instead you choose not to deduct the premiums, then the benefits can be received income tax free.