Generally yes. If these lawyers came out and said "we are recommending that the sentence be reduced because the defendant is a friend of the president," that not only looks bad, but puts evidence of corruption in the legal record books. Moreover, though, a lawyer can not release information to the court without their client's permission. Rather than lie for the government, they recused themselves from the case.
Ultimately, the mere act of all four recusing themselves was a big enough deal that it has snowballed into a major push against Barr, so I think their actions carried significant weight and that further action would not have yielded anything more significant. Attorney-client privilege is a fundamental part of being an attorney, just as the Hippocratic oath is a part of being a doctor. You never did answer my question, but this is essentially the heart of the argument anyway.