There is nothing to be embarrassed about, really, please let us check snappy attitudes at the door. Linear algebra is math considered to be well beyond the scope of precalculus.
http://en.wikipedia.org/wiki/Linear_algebra
Linear algebra is central to both pure and applied mathematics. For instance, abstract algebra arises by relaxing the axioms of a vector space, leading to a number of generalizations. Functional analysis studies the infinite-dimensional version of the theory of vector spaces. Combined with calculus, linear algebra facilitates the solution of linear systems of differential equations.
No one questioned his credentials, although I don't see how that is relevant in the first place.
The term "Linear Algebra" has simply been confused with high school algebra. A reasonable mistake, but still a mistake at that. I would rather be corrected on an online discussion board than in person--but that's just me.