So employees earn more, and restaurants spend less. And this is bad because?

Well, the money doesn't appear with magic, so someone is paying: the government (forfeiting taxes) or the consumer (more pressure to tip).

To me, the bad part is the tax reductions only appear in behavior I don't agree with: high overtime and tipping (when it's semi mandatory).

I'm not American, but this is also showing up in my country.

Because you're artificially favouring one specific industry, at a cost to all other industries.

And because the implication of your argument is we should never tax anything because that's a benefit to both the consumer and the business

Aren't we already in a manufacturing hole and we're incentivizing more service industries over them?