Quote a filename in a script passed to chmod?
fwiw, find [options] -print0, when used in conjunction with (piped to) xargs -0 [options], handles filenames with spaces, without messing with for loops or IFS:

find /Users ! -path '/Users/Shared*' -type f -print0 | xargs -0 -I {} \
    bash -c 'if [[ "$(file -b --mime-type -- "{}")" = "application/x-mach-binary" ]]; then
                 chmod 700 "{}"
             else
                 chmod 600 "{}"
             fi'