Say that one side of a trial brings a witness Walter onto the stand. If the other side doesn't like Walter's testimony (and wants the jury to not take it seriously), are they allowed to engage in character assassination of Walter? For example, airing his past crimes, his controversial social media posts, etc.. To be clear, there is nothing material against the content of Walter's testimony. All they're doing is "factually" berating his character.
As a follow-up, when cross-examining the witness Walter, is the attorney allowed to proceed down a line of questioning designed solely to twist the knife on the character assassination angle (as opposed to questioning about the actual testimony that was made)? For example, directly asking Walter about controversial tweets they made supporting Nazism, as opposed to anything relevant to the case.
I'm not sure what the correct answer might be. On one hand, knowing that the witness has been untrustworthy in the past is pertinent information to be considered by the jury. On the other hand, focusing on a witness's unsavory beliefs is a massive and immaterial distraction that puts personal bias over actual facts.