Crusaders haven't existed for over 600 years. Jihadis are currently staging a coup. So why's everyone picking on Crusaders?

Proabably because they are leftist dimwits.

Crusaders were a just response to hundreds of years of violence from muslims. Do some research and learn history.

You're right. The point of this meme is to criticize people who still go on about them, use them tar all Christians with the same brush or use them as a symbol or byword for religious extremism.

Because Crusaders don't blow stuff up whenever someone insults them.