No, it's semantics. You said that vegans follow speciesism--which is about the different treatment of species, which they do not. So it does dispute what you said.

You're argument is much bigger than what veganism is, which is about animals not about the human's impact on the whole world and all the issues it faces with the environment or the whole ecosystem. Veganism is one issue. For example, yes, veganism reduces the environmental impact based on animals, because it is better for the environment, and you can be a vegan for environmental reasons. But this is not the same as focusing on another humanitarian specific to plants or other organism . If that were the case we'd be talking about the exploitation of farming crops or reducing the introduction of invasive species to certain areas.

We're taking about animals. It's like I'm talking about women's rights, and then you ask, "But what about trans rights?".