There is no law in the UK that covers defamation of a group of disabled people. I tried for a year to get a "human rights" lawyer interested
As a general point, the law on the UK on disability that might sort-of-apply is in three categories - none of which apply.
Judicial review - A review of a decision of a public body (none involved).
Disability hate crime - any crime, due to hating the disabled, or a group of them. (no specific crime has occurred).
Libel/slander - while this is a criminal offence, proving it is hard, and the lie told must be both knowing, provably untrue and of a specific person causing them damage.
Then there is the more general non-criminal sanction against a doctor - 'bringing the profession into disrepute' - this is where the doctors registration body in the UK agrees that the actions fell so far short of what is expected of a doctor in public life that they are no longer fit to practice.
The first three don't apply, as the narrow category each accepts does not apply in the case of someone making arguably incorrect speeches.
The last is extremely problematic and probably practically impossible unless you can get a sympathetic review board, and this seems unlikely at the moment.