What does "defending Islam from it's enemies" even mean?

It's about "defending gods word", and make sure others can't make you "stray from the path". It's literally "defending" against free thought.

The bible has similar things about "defending the word", and killing people who don't believe and so on. But like islam, most people ignore those parts.

He must be devoted to the trustworthy message we teach. Then he can use these accurate teachings to encourage people and correct those who oppose the word

Titus 1:9

The latter do so out of love, knowing that I am put here for the defense of the gospel

Philippians 1:16

If they obey and serve him, they shall spend their days in prosperity, and their years in pleasures. But if they obey not, they shall perish by the sword, and they shall die without knowledge.

Job 36

Always be ready to give a defense to anyone who asks you for a reason for the hope that is in you.

Peter 3:15