Did Constantine Describe the Yahudim as Having "Defiled Their Hands" and Being Blind in Soul?
Source: Constantine's post-Nicaea letter in Eusebius, Life of Constantine 3.18
What the ancient record says
The language becomes much more severe than calendar differences. The traditional translation says the Yahudim had "impiously defiled their hands with enormous sin" and were "deservedly afflicted with blindness of soul", hostile religious rhetoric from the Roman emperor.
Different from Justin/Melito because Constantine was emperor (not that every statement became criminal law, but the speaker now held imperial authority, a dramatic change in context). His letter combines accusations: associates them with guilt concerning the death of the one he calls their Lord, claims they lack sound judgment, and accuses them of calendar error, both theological and calendrical.
"Antisemitism" is a modern analytical term (useful in analysis, but show Constantine's actual language first, what he called them, his accusations, his policy conclusion, then discuss terminology separately).
Read it for yourself. Eusebius, Life of Constantine 3.18.
Evidence strength: Directly attested in the preserved letter. Strong: severe anti-Yahudi rhetoric tied to the Pasakh separation. Separate question: how accurately Eusebius transmitted every word.