Can you imagine if you ask an engineer "what's your opinion on the maximum load this bridge can take?" he answered "for a fee, I will claim that my opinion is what you tell me". In any other profession this would be corruption, but when it comes to lawyers that's their job. Intellectual prostitutes.
When we talk about lawyers for companies and billionaires it's a completely different game.
Remember last time a lawyer said they wouldn't represent facebook because they didn't necessarily believe their innocence? Right, never happened. Because on that league, the game is to twist the meaning of words so much that the judge starts to doubt he understands the law himself.
Thanks for reinforcing my point.
To be fair, the deviation from the truth an expert witness may grant tends to be bounded. Whereas the deviation a lawyer may attempt is unbounded. In many cases the bounds don't matter much as the case contains sufficient uncertainly to be a contest of spin targeted at the psychology of the jury.
With lawyers, paying to defend a side is the whole point.