"When he remarks that he has been dumbstruck by Christian and Moslem intellectual commitments, I believe the word has met the man"
Remarks about the translation
If it does help, the whole paragraph is:
"At the beginning of his Letter to a Christian Nation, Sam Harris writes that his fiercest and most “disturbed†critics are Christians who are “deeply, even murderously, intolerant of criticism.†It would seem that a good many of those intolerant critics have been sending Harris biblical verses supporting their intolerance. Now, I count myself among Harris’s warmest detractors. When he remarks that he has been dumbstruck by Christian and Moslem intellectual commitments, I believe the word has met the man"
Instead of "abismado com" I would say "atordoado pelo". Dumbstruck would mean like the feeling of being hard hit by something that makes you "dumb". Instead of "conheceu o homem" I would say "encontrou o homem."
I thınk ıt could be: "Quando ele percebe que tem sido emudecido pelos compromissos intelectuais cristãos e mulçumanos, eu acredito que ele compreendeu(caiu na real).