My current CPA believes there is an incurred 39% tax if I switch to a SDIRA and has warned against doing so. Is this true?

No.

Your CPA is likely not as familiar with the SDIRA process as a specialized firm would be. They may also be under the assumption that you are attempting to take an early distribution from your current IRA in order to fund your SDIRA. This is untrue. Opening a SDIRA is typically considered a custodian-to-custodian transfer of your current IRA. Because of this, the startup process and investments are non-reportable and non-taxable.