The case made for that is distinctly underwhelming.
> Bail bonds are a legal service.
That doesn't mean Google needs to carry ads for them.
> Indeed, they are a necessary service for the legal system to function.
No, they aren't. They are a necessary service for the abusive system of excessive cash bail to function, but the entire system of cash bail is facing widespread (and not along traditional party lines) criticism as being incompatible with the fundamental values of our legal system.
But even if this description was accurate, that doesn't mean Google carrying advertising for the industry is necessary.
> Whatever the cause, preventing advertising doesn’t reduce the need to pay bail it simply makes it harder to find a lender.
No, it doesn't, as doing a Google Search for “bail bonds <city>” and comparing the advertising results, map results, and organic web search results would show.
> Restrictions on advertising in the bail industry, as elsewhere, are also likely to reduce competition and raise prices.
The source cited for the argument for the general effect here studied effect of advertising taxes, which increase the price for equal visibility; whether the Google ban is in any way comparable really depends what the main mechanism is for people finding bail bonds through Google-placed ads. If it's mostly search advertisement on relevant terms, banning the ads gives organic results the same effect that paid ads use to have, and reduces the cost of visibility, which would have the exact opposite effect of an advertising tax. This would, therefore, be expected to increase competition and lower prices.