I was just talking to an elderly lady who has well over $1M in equity in her house (not that uncommon for Hawaii homes). A tax on her equity would destroy her.
If she had no deductions for repairs, maintenance, or remodeling which is unlikely, and her income is within the 15% capital gains tax threshold, with the first $250,000 reduction, her Federal capital gains tax would be $112,500. In addition Hawaii's long term capital gains tax is 7.25% which on 1,000,000 $72,500. This means she would owe a total of $185,000 in state and federal long term capital gains on her real estate. She would still have a net equity of $815,000. Also, she can avoid paying capital gains tax by buying another house and using the 121 home sale exclusion.
If she doesn't already have a financial/estate planner, she'd be well advised to consult with one prior to selling her property.