Answer
The person is probably misunderstanding the meaning of a "scientific theory" vs. a "hypothesis".
In everyday life, these two terms are often used interchangeably, i.e., a "theory" may be nothing more than a speculation. However, in science, a theory is "a synthesis of a large body of information that encompasses well-tested and verified hypotheses" ("Summary of Terms", page 17 of textbook) and is on very solid ground.
