The problem with the joke is it’s targeting An easy group to make fun of. Tourette’s is a complex condition and most people don’t understand it - they just think a sufferers inability to control their words or actions is some bizarre life choice.
Secondly it starts in childhood - and children cannot speak up for themselves as adults can. How many other childhood illnesses get laughed at?
Thirdly not one of those other jokes targeted a minority issue. Not a single joke about Transgender people. No one would be brave enough.
Do you remember the last time you laughed at a person with Parkinson’s/ Dementia/ Cerebral Palsy - of course you don’t.
My children hide their Tourette’s in public precisely because of attitudes aligned with this joke. Most of our immediate family won’t even acknowledge their illness because our relatives are so conscious of the stigma.
It’s not being professionally offended, it’s being sick of the some people’s attitude to one condition that it is still acceptable to make fun of.
That’s why it’s offensive.