So you feel that Mexico was justified when they decided to wipe out the majority of the population of Texas in their campaign against the rebels in 1835?
I think that when nations are at war, bad things happen and people get hurt. Nothing new there. It's been going on for thousands of years.
I would say that it is only in the past century or so that people have decided that wars shouldn't involve pain or suffering. We should have nice wars and try to get our enemies to like us. This is why we haven't really won a war since 1945.
I really do see illegal immigrants as an invading army. It really does bother me that these invading soldiers do not wear uniforms.
Was Mexico "justified" in killing Texans in 1835? I don't even know what that means. All I know is that Mexico behaved in a standard way as it tried to claim land where other people lived. It's the way of the world. The United States is foolish for getting into that arena but trying to play the game in accordance with polite little rules that no one else wants to follow.