I disagree that parsing is validating. For example, you could give me a valid ISO date time string, but I want a shipping date and you gave me something in the past. It parses, but is not valid.
I disagree that validating early is bad because some other part of the code might also validate later and possibly do it differently. Yes, that's bad, but not a reason to not validate early.
I don't see it. I would much prefer to validate early rather than late. The example of 'other code might validate it differently or not at all' seems specious. I don't want invalid information "deep within the bowels of the system".
Do I need eight arms to use it