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. I wouldn't go as far as to call it a riot—I think it was just a bunch of rowdy kids causing trouble.

go so far as to (do something)

To do something extreme, risky, or controversial. Often used in the negative. Although I wouldn't go so far as to call him a coward, he definitely likes to avoid confrontation when he can. They went so far as to threaten us with legal action if we didn't delete the video in question. I wouldn't go as far as to call it a riot—I think it was just a bunch of rowdy kids causing trouble.

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.