It takes a fantastic will to unbelief to suppose that Jesus never really 'happened', and more to suppose that he did not say the things recorded of him -- so incapable of being 'invented' by anyone in the world at that time: such as 'before Abraham came to be I am' (John viii). 'He that hath seen me hath seen the Father' (John ix); or the promulgation of the Blessed Sacrament in John v: 'He that eateth my flesh and drinketh my blood hath eternal life'. We must therefore either believe in Him and in what he said and take the consequences; or reject him and take the consequences.
From the same letter -- written, remember, in '63, just before Vatican II got into gear -- this prescient observation:
I suppose the greatest reform of our time was that carried out by St Pius X: surpassing anything, however needed, that the Council will achieve.
The 'reform' he refers to is not made fully clear in the text, but the editor of the collection of letters notes that, given the context, it was probably Pius X's exhortation to receive the Eucharist daily.
'Surpassing anything ... that the Council will achieve'? How right he was!