This provides good context: https://astralcodexten.substack.com/p/effective-altruism-as-... EA is a very very tempting horse to beat, to the point it's their own internal favorite sport. There are large quantities of ink spilled criticizing it, from inside and outside. But it is all pretty worthless without taking a look at the foundations of the movement.
"I don't think AI is a risk, so I'm opposed to EA" charitably means that that person is opposed to EA, the organization headed by the people named in the article, and the choices they have made, who have made themselves the face of the movement with the same name. It doesn't mean they think that helping people is bad.
It's one of those fun language tricks groups get to play when there's a movement of some sort, and then a specific organization pops up with the exact same name. Black Lives Matter famously did the same thing; great movement, but the organization with the same name has done some questionable things with the money they were given.