Did you read the article you just linked to? Here's a direct quote "From a social welfare perspective though, first degree [perfect] price discrimination is not necessarily undesirable. That is, the market is entirely efficient and there is no deadweight loss to society."

Without price discrimination, unless you're operating tax-free and subsidy-free there is always a dead-weight loss. Perfect price discrimination eliminates it. It is literally right there in the article you just linked to.