Really?
I would guess you have zero understanding of what the senator was ever talking about do you.
Cornyn is definitely in the doghouse with his recent betrayal of his constituents with gun control, but he's not out of line with this. The comparison between Board of Education overturning Plessy appeared just a few years after the Roe decision, at least in the pro life movement.
He can be criticized for giving a meme to the left to dupe their low-information (and dare I say low-intelligence) voters, but he's solid on the substance. It's not a new comparison by any stretch of the imagination.
At the risk of being tedious, the left suddenly became fans of stare decisis (turning pretty much on a dime). The obvious retort was to point out that the left loved Board of Education, and had cheered when that opinion overturned decades of "separate but equal" doctrine that pretty much everyone agreed needed to be fixed. It was a chance to demand some measure of consistency from the left, which they hated at the time.
That's what Cornyn was referring to.