Environmentalism would be better served if environmentalists focused on deeper solutions and did not waste societal attention and resources on distractions of negligible outcome. Black-and-white thinking and choosing to die on every hill only serves to breed false self-satisfaction and alienate potential supporters.
We need to think about a world without throw-away plastic. Banning plastic straws is an exploration in to that world. If it turns out that there is absolutely no way to live in a world without plastic straws, then I am sure the ban will be undone. But I think we can get ahead of this challenge, it’s not that big.
There's no reason why the needs of disabled people must conflict with taking care of the environment. The apparent conflict in this situation was introduced because people developed their environmental policy proposals without any awareness of or care for the interests and needs of disabled people: if we do not account for the effects of policies on disabled people when deciding which policies to prioritize and how to implement them, some policies will look artificially more appealing because of our inattention to some of their costs and the policies we do choose to pursue will end up implemented in needlessly harmful ways simply because we weren't paying attention to whether we ended up causing harm to some people.
The scope of people you mention with that disability is very very small. And still, they could work around metal by using a piece of rubber on the tip. Hell, someone could invent a special straw just for disabled people (we could make it longer and more flexible, you might call it a tube!).
Instead of ripping apart my lay ideas and complaining about our attempts at fixing climate change, perhaps we ought to be thinking of better solutions for our friends with disabilities. Because ultimately, climate change will take the lives of people with disabilities before it takes the lives of able-bodied people.