Well... I would argue that the statement is sexist if it can be perceived by the receiver that it is sexist. It does not matter what the state of mind is of the person uttering the comment. What matters is how it was received. And the evidence we have is that the receiver WAS offended.
This is a festering illness of our age.
You can tell me how you
perceive something someone says, but absent a very explicit expression by the speaking party of their intent, no one can state what the speaker's intent, motive, was.
This is especially important in matters such as the subject at hand or (for example) issues of race; not every person is attuned to each and every means of offense, some because of poor educational attainment, some, because of lack of cultural awareness, some because they simply lack the mental faculties to recognize nuances.
It is useful (and sometimes important) to tell someone who has said (or written) something which has been perceived as offensive that such has occurred - one will most often find that the speaker had no such intent, and will wish to clarify and thus discharge the offense (and, in the process, perhaps learn something they did not theretofore know).
In any event, if I hear or read something which could be interpreted as either an offense or an innocent statement, am I not obligated to at least extend to them the courtesy of presuming no offense was intended until I learn (from them) otherwise before calling them out?
If I do not extend that essential courtesy, while the other person may have unintentionally caused offense, I will most certainly have done so in a much greater quantum and with absolute intent, and that would make make me the greater villain.
Be kind to others.