The letter writer herself actually solves this better than Prudence.

First, let's not pretend that the romantic choices a potential new mate made in the past have no bearing on how a new relationship proceeds. If you found out on a first date that your companion's (I'm a man) ex-boyfriend was president of the College Republicans, and you are a die-hard Democrat, clearly you would be right to question whether your values meshed.

The writer states that she herself agrees with some of her new boyfriend's views on the character of her 'ex'. She simply has to convey to her new beau that she finds real value in their current relationship- value that she clearly did not find in her relations with the former man. In essence, make it clear that she relates more to his character traits than her ex's. Men get this, end of discussion.

Prudence first makes the mistake of assuming, three-times removed, positions held by the new boyfriend - & then she offers advice on those assumptions. & the advice she gives basically calls for the writer to first bring up the thorny issue anew, and then stonewall any response! This will only give the impression that she had no problem whatsoever with the former man's character - which is at the heart of the issue & contradicts what the writer herself indicated about her views.

Following Prudie's advice in this case will effectively end a promising relationship.