You can legally murder people to prevent "mischief", as long as it's at night? Wow.
Mischief is typically a serious crime; the legal and common uses of the word are different and confusing.
But I don't think Texas is restricting this to the more serious felony mischief here.
The first two clauses are destroying property and damaging property in a way that causes pecuniary loss to anyone.
The third clause is making marks on property. This seems like it would always be included under "damaging property in a way that causes pecuniary loss", so I would guess it's there to make it completely explicit that graffiti counts as criminal mischief.
The quoted section of the penal code does not appear to apply any restrictions to the specific variety of criminal mischief that justifies deadly force (other than that it occurs at night).
For something like graffiti where the general sentiment is that deadly force shouldn't be considered justified, I could see an argument that the use of deadly force violates §9.42(3)(A), which requires the person using deadly force to reasonably believe that the land or property in question "cannot be protected or recovered by any other means". If we view both verbs as applying to criminal mischief, you could make the argument that when you catch someone spraying graffiti on a wall on your property, your property can be recovered, though not protected, by e.g. repainting the wall.
The counterargument might be that "recovered" is in there as the appropriate verb for cases of theft, and "protected" is in there for cases of mischief.
I don't think restricting §9.42 to felony mischief would be an improvement to the law; it's difficult to know whether criminal mischief is or isn't a felony until you've tried to recover from it and learned how much that will cost. If you catch someone keying your car, for example, that probably is a felony, but as far as social impact I would rate it similarly to graffiti.
Note that the harm to the victim is identical in both cases, except that in the case of theft, recovery may be possible.
You can't have a functioning democracy if it's impossible to criticise the current setup. This is the whole idea behind newspeak [1]
Unjust according to whom? Wouldn't it be better to just make our premises explicit?
In terms of rhetoric, explicitly adding "I believe that..." to the beginning of a statement softens the statement to a degree that the speaker may not desire. When a vegetarian holds up a sign saying "Meat is murder" I don't think very many people are confused about "according to whom" or that they think the person waving the sign believes that killing animals is actually against the law. "I believe that killing animals for food is immoral and unjustified so we should stop" certainly lacks the punch of the original statement, and the number people who are confused about the original statement is small enough to justify the punchier language.
You expect pigs to defend you?