Contradiction with Romans 12:18
Nehemiah 4:8 shows a strategy to fight against adversaries, which contradicts Romans 12:18's encouragement to live peaceably with everyone.
Romans 12:18: If it be possible, as much as lieth in you, live peaceably with all men.
Contradiction with Matthew 5:44
Nehemiah 4:8 describes preparing for defense against enemies, whereas Matthew 5:44 suggests loving and praying for enemies.
Matthew 5:44: But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;
Contradiction with Exodus 14:14
Nehemiah 4:8 involves actively preparing for battle, while Exodus 14:14 emphasizes standing still and letting the Lord fight.
Exodus 14:14: The LORD shall fight for you, and ye shall hold your peace.
Contradiction with Proverbs 20:22
Nehemiah 4:8 shows intent to retaliate against threats, which contradicts Proverbs 20:22's instruction not to say, "I will recompense evil."
Proverbs 20:22: Say not thou, I will recompense evil; [but] wait on the LORD, and he shall save thee.
Contradiction with 1 Peter 3:9
Nehemiah 4:8 involves responding to aggression with defensive plans, against 1 Peter 3:9's advice not to return evil for evil.
1 Peter 3:9: Not rendering evil for evil, or railing for railing: but contrariwise blessing; knowing that ye are thereunto called, that ye should inherit a blessing.