You are wrong; Baptism is not the only Sacrament “necessary”. What is necessary for salvation is to love God with all of your heart. “If” you do indeed love God with all of your heart, you won’t be concerned with what the least you need to do, you’ll want to do the most you can do. If God gives you a gift do you joyfully accept it because of your love for Him? Or is rejecting His gift showing your love more? God gives us seven wonderful gifts in the Sacraments, no, you don’t “need” to, and most people will never, receive them all. Does that mean we shouldn’t want all we can? God gives you a wonderful gift of reconciliation (confession), should we joyfully accept His gift? Or make excuses to try to avoid His gift? God gives us His body, blood, soul, and divinity in the Eucharist, should we joyfully accept His gift? Or try to figure out ways we don’t need it? I know we are only human, and our minds certainly not Gods’, but, if you offered your family the sacrifice of your life, and they said no thank you, how would you feel?
You should not kill someone for destroying the Eucharist; you could however offer your life in defense of the Eucharist.
It would be a sin to intentionally bare false witness, knowing full well that it is a grievous offense toward God, knowing the lie separates you from the grace of God, and fully accepting this separation from God and its eternal consequence.