The whole fruit/vegetable controversy only comes because we're trying to use two different domains of terms interchangeably: botanical terms and culinary terms.

Tomatoes (and squash, and pumpkins (which, side note, are a type of squash), and cucumbers) are botanically fruits, but culinarily they're most commonly used as vegetables because they tend to be less sweet, particularly when raw. Mushrooms are botanically...well, I guess they're botanically "n/a", as they're not a part of the plantae kingdom, but whatever--they're typically considered botanical, so they're "botanically" fungi, but culinarily they're most commonly used as vegetables (or, interestingly, as meat replacements).

We get into the same linguistic confusion when we start throwing around "peanuts aren't nuts, they're legumes!"--botanically, yes, peanuts are legumes, but culinarily they're most commonly used as nuts. See also: "green beans" are botanically pods, not beans, but we use them culinarily as vegetables; and many "berries" are botanically something else but we use them culinarily as berries; meaning they're often left whole, mixed with other berries in the same dish, and go well with cream in cold summer desserts.

The whole thing is a misguided exercise in pedantry; "technically burritos aren't sandwiches, they're meat-sacks!" They're both, and we instinctively understand that trying to compare the two terms is silly because "sandwich" is a culinary term and "sack" is not.

~~Another funny part of this is that pedants are trying to say that tomatoes are (botanically) fruits and not vegetables, but the closest thing to a definition we have for "vegetable" botanically is "literally all plant life and maybe also some fungi," so tomatoes are clearly both fruit and vegetable botanically.~~ Plus, they're culinarily used as vegetables, but can also be used as fruits in some cakes, pies, sorbets, and so forth (and isn't ketchup just a tomato smoothie?), so tomatoes are clearly both fruit and vegetable in culinary terms as well.

edit: Someone who actually knows what they're talking about (an ecologist) has corrected my botanical definition of "vegetable." Actually, they're “edible parts of a plant which are not fruit.” Which means that tomatoes are explicitly excluded as vegetables, being botanically a fruit. I don't think that ruins my overall point in any way, though.

Leave mycelium alone

Actually, "mushrooms are technically meat" is a new hill I'd like to die on. Mushrooms have animal cells, ergo, definitely not a vegetable.

Big Mushroom is going to take out OP, Boeing-style.

Always dismiss those people who talk about how tomatoes are fruits as nerds. The category "vegetable" in the kitchen usually refers to more savory plants, not that what part of the fruit it is. Also if you're still one of those "um, ackchually, tomatoes are fruits" kind of people, then eat tomatoes like apples. Maybe even some chili peppers too, they're berries.

Sure, but they are fun guys!

Yeah but a mushroom's such a fungi to be with.

The true misconception is that there are scientific definitions and culinary definitions. No the culinary definitions don't fit their scientific category. They're not intended to.

They’re (mushrooms) also constantly listed on American menus as a “protein” option despite a dire lack of the stuff

Fungi only got its own kingdom in 1969, before that they were a phylum in Plantae. There are tons of people still around who learned "mushrooms are plants" in school, so it's not surprising downstream vocabulary hasn't caught up.

Vegetables are a social construct. Depending on culture this is differently labled. Afaik there are No vegetables in a botanical sense. Just "fruits".

That's because Vegetable is not a Botanical Term. It is a culinary term. So, Tomatoes are both fruit and vegetable.

Strawberries, blackberries, mulberries, and raspberries are not berries.

Bananas, aubergine (eggplants), oranges and grapes are berries.

Dangleberries aren't real berries either.

Let's not forget that apples, strawberries and cashews are pseudofruits, just like the produce of my labor!

"Are red pandas carnivores or herbivores?" "They eat like 80% bamboo, so herbivores." "Wrong! They are taxonomically in the order carnivora, making them carnivores! Please ignore that carnivore also just means meat eater and herbivore isn't even a taxonomic clade. People only ever talk to me to get mad at this switching between casual and scientific definitions, I am nothing without it."

"Fruiting bodies," even

I don't think I've ever considered a mushroom a vegetable, they're just mushrooms

Mushrooms are obviously fruit