I think that's a pretty awful way to treat people. Why do you care what vegetarians/vegans eat? Why attack them?
Every now and then it's fun to have a quorn "buffalo patty." It satisfies a desire of mine for something like that. But I don't have to eat healthy in order to be a vegetarian or vegan. I don't have to make health food my choice to be either vegetarian or vegan. I can simply be grossed out by animal products, or any other reason that results in me not eating/using animal products. My reasons for the way I live my life are mine, and yours are yours. I don't ask this person to explain their life nor dietary choices, so they shouldn't bother with mine.
The general format is about picking a subject (person, brand, company, political party, country) that they are ideologically hostile to, and then picking bits and pieces from the Internet that show that it is baaaaaad. Not that it has a particular downside, but it's baaaad because maybe A, looks like B, I think C, and I heard that D. In this particular piece: the base is not a mushroom (who cares?), Quorn is successful (get'em!!!), I don't like how it tastes (good for you?), and it's owned by a big corporation (see, told you they're evil!). Also, other companies selling fake meat use very complex recipes (you don't say...).
None of that involves actually talking to people or scouting publicly unavailable documents, which is what I perceive as journalism. And they have the guts to claim that "The Guardian’s independent, investigative journalism takes a lot of time, money and hard work to produce."
It’s a warm blanket and a bottle of milk, not great journalism.