Still not sure with so many of the (esp right leaning) in the US claiming to be christian, can also accept this as a punishment. But I get nonsense begets more nonsense.
There's also testimony of Jesus disrupting an instance of capital punishment (John 8:3–11). There may have been procedural issues in that case, of course – for example, no accusers are said to have claimed witness to the crime itself, which was legally required for an execution – but Jesus points this out after the mob has dispersed, not before, and many Christians interpret that verdict more generally.
In modern legal theory, we have a similar distinction, which you may know from Legally Blonde: malum in se (that which is inherently wrong) and malum prohibitum (that which is wrong because a lawful authority prohibits it). Example: endangering the safety of others by driving too fast is wrong in itself, while breaking the speed limit is wrong because the town said so.
The former type (moral, and in se) doesn't depend on the existence of a government or system of laws and justice. The latter type certainly does, and the wrongness of those things 1) is changeable at the will of the governing authority, 2) applies only to those properly under the authority, and 3) expires when the governing structure expires.
Christians believe the ten commandments are moral law, whereas when we get into the ins and outs of the ancient Israel system of justice, described at length in Leviticus, eg, we are seeing one civilization's implementation of that moral law into civil law, coupled with religious law and ceremonies that symbolized and pointed to deeper realities.
When Jesus says he does not abolish but fulfills the law (and he means all of the law, not just some laws), he can't mean you are now free to murder. He means if you murdered someone, you may yet receive eternal life and not eternal death, because he can pay the penalty on your behalf. He means he lived a perfectly moral life and can impute that to you. That's fulfillment of moral law.
It also doesn't mean eating pork was immoral and now it's moral. That dietary restriction was a malum prohibitum component of the ceremonial cleanness symbolism that was meant to point the Israelites to the reality of what happens to a soul that consumes unholy things. It was never immoral, only prohibited. But the law is fulfilled in that the symbol is no longer required. Jesus institutes a new symbol that fixates on his own holiness and cleanness imputed to us as if by eating it (the Lord's Supper). The early Christian movement quickly incorporated non-Jews who had no heritage of living under the authority of the Israelite state, which was, by this time, already expired/expiring, many times over through successive conquests and occupations by various other governments. Neither the non-Jewish Christians nor the Jewish Christians needed to abide by those laws, though many did for a time, as it was an integral part of cultural and religious custom.
Though, Jesus was subject to capital punishment, despite the original prosecutor (Pontius Pilate) claiming no lawful basis for the execution (Luke 22:66–23:25). This was presented as unjust, despite Jesus' insistence that it had to happen. This is a bit muddled as an analogy, but I see how some people might take "capital punishment is wrong" from it.
Anybody who professes to be a Christian or follower of Christ’s teachings who supports violence in any form is in fact living in contradiction.
It's not the christianity per se that makes them bloodthirsty. Contemporary american evangelical christianity is a novel social-political-religious movement and in some theologically significant ways has broken with near-universal christian tradition. Trying to understand it purely as a religion is too incomplete.
We really should call them "dysangelical" when they bring death like this (as opposed to warning of death, which is in scope of euangel when there's also a way to avoid it).
You shall not kill!
What I don't understand. It is my impression that most of the US states that still have the death penalty, strongly oppose abortion. I find this a contradiction. And also these are the states that oppose abortion, at the same time are strictly against any kind of welfare "not our problem!".
I think it’s a question of agency. If you’re an adult that makes their own choices (crime, bad financial decisions, etc.), then you know what the consequences are.
If you’re an unborn child, you’re don’t have agency.
For some there’s probably deeper religious belief in good things (birth) being the work of God and bad things (crime, vice, death) being the work of Satan.
To your point there are plenty of competing religious teachings that could lead some to be pro-choice, pro-welfare and anti-death penalty.
The problem with your assertion is that you don't understand the rule book ( Murder is not the same as capital punishment.), and you have nothing for contempt for the said rulebook.