He believes that the public holiday of Christmas deserves respect and attempts diminish the holiday by refusing to say `Merry Christmas' or restricting Christmas traditions are wrong.
(grammatically correct or not)
not
"He believes that the public holiday of Christmas deserves respect and attempts to diminish the holiday by refusing to say 'Merry Christmas' or restricting Christmas traditions are wrong." is correct.
"He believes that the public holiday of Christmas deserves respect and that attempts to diminish the holiday by refusing to say 'Merry Christmas' or by restricting Christmas traditions are wrong." is clearer.