yes, I agree. there are many passages that show us that we are not to walk in that way. I think the clearest is when Jesus spoke about living by the sword to Peter.
But again, WHY do you practice it. I don't believe God is ok with us being unhealthy and not taking care of this temple. for me, it's fitness, I don't intend on ever using it on anyone. then again, I practice something very unorthodox that isn't even understood in the typical martial arts world. but I also feel like the situation or context changes it. example, say someone breaks into your house and is coming after your kids or wife, will you stand there and let it happen? I would argue that you are not being a proper man of God and husband if you are allowing that to happen. I'm not saying you have to destroy the guy, just saying you should know how to contain him and prevent it. as a man, we are protectors, we should know how to protect.
now the flip side. if the same scenario happened and you were not present and something happened, now you must deal with forgiving that person and showing them the love of God. You have a responsibility to your family, especially being a man of God.
now the spiritual side of it, there is war in spirit when we pray for people, spiritual warfare is very real. we are going to be in the army of God fighting in the end times. God is for fighting, just not the type we think about. we should not dedicate our lives to hurting others or be training this intention or reaction, I don't think that's biblical at all. Jesus went into the temple with a whip, he wasn't exactly tickling them. but again, look at the context, its WHY he did it. it wasn't for self defense, it was for justice, BIBLICAL justice, not carnal and fleshly in nature, but spiritual. you feel me?