One of the problems is the common phrase “original intent,” which allows people like your progressive friend to say “we cannot know intent.” (OtoH, his standard – “evaluate cost and benefits” has its own problems – costs to whom and measured by what standard, and benefits to whom and measured by what standard? – Essentially it’s an argument for unlimited government, unlimited discretion in the hands of judges; de-legitimizing the very constitution from which these judges/officials ostensibly get their authority. Without the constitution, they’re just a bunch of tyrants whose authority is backed only by naked might. Which, at least to many people here, would at least be revealingly candid).
I don’t think your friend would hold the same standard for speech/expression (“lets evaluate the costs and benefits – by some arbitrary standard – and forbid speech where the cost is determined to potentially outweigh the benefits) (potential is the only way to measure such things prospectively).
Note also that in the long history of government evaluations of what the costs are and what the benefits are of any measure or policy, their record of accuracy is. . .poor.
(ending this post because I meandered).