This is an antitrust case. Google's competitors are victims of the alleged monopolistic behavior. If you're going to make the analogy right, then the alleged crime needs to be that you defrauded your neighbor's business. I can't imagine a court barring your neighbor from testifying that you defrauded him just because he'd benefit financially from a ruling against you.

The person testifying in this case is the CEO of the company that runs the second largest search engine in the country.

The trial is about if Google used illegal practices to suppress and harm competitors.

So the person testifying, literally, is the victim of the crime.

> It's an opinion from someone who hates you/benefits from convicting you.

Hence why the opposing side gets the opportunity to cross-examine the witness, and why it would be a really bad idea to put forward a witness who clearly has a grudge against the accused. In cross you just show they have a grudge and now their testimony is suspect.

> Now, if they had actual evidence it'd be different

It is actual evidence. I don't think you know what evidence is...