He may be referring to the fact “a lot” was used in there. “A lot” is a singular.
Of course, we could cry “BRITISH!” and use the abuse of “the enemy have” and “the enemy are” as rationalizations for saying “are a lot”.
“A lot” is used here as an adjective, isn’t it? “Rumors” seems to be the subject.
Reminds me of saying “The media are” when it would seem more logical to say “The media is”, but “media” is plural, n’est pas?