What meets the legal definition of harm for speech has no bearing on whether you can inflict harm on someone else in response to something that does not meet that legal threshold of harm. For example there is no scenario in which you can defame someone because they said something mean, whether or not what they said meets the legal definition of harm. You can’t libel someone back for libeling you.

> As for actual bloody harm. In the US not only you are allowed to defend yourself in case of an agression, you are supposed to, and you are given the tools to do so (i.e. guns). In several state, you can shoot people trespassing

None of this is true for the US. You do not have a duty to defend yourself, in fact it is the opposite. You have a duty to retreat, and only if there is no reasonable avenue of escape without putting yourself more at risk do you have the right to strike back in self defense. The Castle doctrine you are referring to re: trespassing is a merely an exception to the rule, in which you do not have a duty to retreat within your own home. You still must meet the other requirements for self defense and can only respond with a level of force proportionate to the perceived threat.