That seems to be a pretty weird view to me.

If you're convicted of crime X, you should be sentenced base on crime X, not on what other things everyone believes you actually did, but for which sufficient evidence can't be found to convict.

You seem to be advocating for a legal system where it's fine to punish people for things they haven't actually been convicted of doing. Regardless of what we may think of Al Capone, or "know" that he did, I think I would much rather let an Al-Capone-type off with the comparatively light sentence of a tax-dodger, than risk a harsh sentence for someone who didn't do the unproven things that people nevertheless "know" they did. Because of course that will happen.