go as far as to (do something)
To do something extreme, risky, or controversial. Often used in the negative. Although I wouldn't go as far as to call him a coward, he definitely likes to avoid confrontation when he can. They went as far as to threaten us with legal action if we didn't delete the video in question.
go so far as to
Also, go as far as to. Proceed to the point of doing something. For example, I wouldn't go so far as to call him incompetent, but he does need supervision, or Would she go as far as to sell the house before she's found another?
go as/so far as to do something
be willing to go to extreme or surprising limits in dealing with something: She’s a brilliant painter, but I wouldn’t go so far as to say she is the best in the country.I don’t like people smoking but I wouldn’t go so far as to forbid it.