You need to decide whether you object because a government option will reduce choice by outcompeting and wiping out private insurers or whether you object because a government option will be like the USPS vs UPS/Fedex. You can't have it both ways.

If you want to object to the proposal, why not focus on guarantees about keeping your own plan or existing insurance, or the issues Tracy H has raised regarding qualifying plans and the requirement to move to one if anything in your current plan changes. Government can set the qualifying standards but the legislation doesn't control what insurers or employers may offer during the five years they have to comply. As it stands you may indeed be forced to change plans even if something as small as your co-pay changes, which happens every year in many plans. Theoretically an insurer could employ such a stratagem to eliminate benefits by forcing unprofitable policyholders onto other plans or even fire them by not rushing to qualify. Not as easy to express as a critical soundbite, but a 100% valid objection IMHO.