I actually agree with this for some parts of it. Theorymon is important for these arguments in moderate amounts, because they help to prove the logic about the actual situation at hand. For instance, if someone was trying to argue that Dragons were the best types of pokemon in the entire game, they could use deductive reasoning (A+B=>C) to argue their point using theorymon.
Eg. A - Draco Meteor is the best move in the game.
B - All Dragon types learn Draco Meteor and no other type does.
C - Therefore, Dragon types are the best pokemon in the game.
Now, while that may prove true in some cases, it's not entirely true with cases such as Altaria. That's the problem with theorymon. It may sound logical, but in practice, that logic doesn't necessarily exist. It also requires much more work to actually convince someone with theorymon, because if you don't have actual proof of what you're talking about, people may find it hard to believe you, and a lot of people using theorymon are not using any sort of proof or logic in their claims, which is why it's being looked down upon so much.
However, when people are not using theorymon for their arguments, AKA using their experiences as their source, it's a lot harder to argue with them. You can't necessarily argue with someone's experiences unless you've been with them through their entire life. You can, however comment on them. People using experiences as their source will have a much easier time to logically think of why those experiences happened, because they actually experienced it, and therefore, they're able to make a much more solid argument out of it since they don't need to provide as much proof.
An example of this in real life could be a boxing match -
A boxer just lost a match against the world champion, but they realize after the match that they were not putting the pressure on their opponent as much as they could have been, and while they were at it, they were leaving their chest unguarded. They do not need to prove this to anyone, because they were actually in the match with the world champion. They know that, logically, if they were to guard their chest while keeping the pressure on their opponent during the match, they would have stood a much better chance, and therefore they will have a much easier time explaining this to someone because it's their experience. This is an example of not using theorymon, and it should show how much easier it is to make an argument when you use your own experiences as your source of proof.
However, a fan that was watching the boxing match may just believe that the losing boxer simply is not as strong or qualified as the world champion, and that because of their body structure, the loser was not as quick as the champ. Now, in order to get people to actually listen to this argument, this fan must find some kind of proof to show that this boxer is weaker and less qualified than the champ, and that their body structure is confirmed to make them slower. The fan decides that this is too much proof to find and doesn't feel like finding it, and when he says this to people with no proof of his points, nobody takes him seriously. This is an example of what is happening when people use theorymon, because a lot of people are using it, but they do not feel like finding the necessary proof for their points, and therefore their argument becomes extremely faulty, and they fail to persuade anyone. If people are going to use theorymon to prove anything, they HAVE to use proof for their points, or just not use it at all.
Basically, in summary, using one's experiences as a source for proof makes it much easier to make a solid argument than using theorymon, which is much harder as it requires a lot more proof, which a lot of people just aren't providing, which is making the authority figures here look down on it.
