I think the reason a lot of leftists struggle with disability justice is that they haven't moved past the concept that discrimination isn't bad because it's objectively "wrong." yes, sexists are objectively wrong when they try to claim women are dumber than men. yes, antisemites are objectively wrong that jewish people are inherently greedy and run the state. yes, racists are wrong when they try to claim that white people are the superior race. and so on.
but then with disabled people, there are a lot of objective truths to the discrimination we face. people with IDs/LDs do fall behind and struggle with certain concepts. physically disabled people are often weaker and less capable of performing demanding tasks than able bodied people. many of us with mental illnesses are more reckless and less responsible. a lot of us are dependent on others and do not contribute much "worth".
and guess what? disabled people still deserve a place in the world. disabled people still deserve the supports they need. because they are people, and that should be enough to support them and believe they deserve a place at the table.
if your only rebuttal against discrimination is its objective inaccuracies, you are meeting bigots where they are at. you are validating the very concept that if and when people are truly incapable of being equal to the majority, that means they are worth less. this causes some leftists to then try to deny the objective realities of disabled people and/or become ableist themselves.
your rallying behind marginalized groups should start and end with the fact that people are completely worthy of life and equity, because they are fellow human beings and that should, frankly, be enough.
