Don't be disingenuous, goodbye - you were using words like 'matrons' in a clearly disparaging and dismissive way.
The sexist bit is the characterization of women as 'uptight' on the grounds that they have no patience or tolerance for jokes they see as sexist. By all means argue that something isn't sexist, but immediately responding with accusations of uprightness - ie it must be down to a woman's character flaw if she objects - is, I'd have thought, the absolutely classic sexist response. It's all a bit 'What's the matter, love, can't you take a joke?', don't you think?