Then what is about?
Where is the strawman? Veganism, as defined by vegan groups, is primarily about the avoidance of a particular class of products and is not rooted in any specific ethical, legal or scientific theory. Now, of course, vegans as individuals may have some "ethical impetus" but that doesn't mean veganism as a doctrine does.
The "not vegan" vegan sect has it's proponents but it's not fair to say that veganism is not rooted in ethics:
"which seeks to exclude, as far as is possible and practicable, all forms of exploitation of, and cruelty
to, animals..."
While the above statement is not rooted in "any specific ethical, legal or scientific theory" the same can be said for just about any socio-political movement, including animal welfare/rights.