Crusade pathfinding

[Boris of Bohemia]

I am playing the Danes. The English attack. I take Scotland, and the port is pillaged.

The English build a crusade in Northumbria, which has a port, and declare the objective of Tripoli.

The crusade moves to Scotland (with no port, I repeat) and asks permission to "pass through". To Tripoli?

Fearing a comp cheat to suck away my huscarl general/govenor, I refuse. I am excommed, of course.

Dumbfounded.

Edit: The sea lanes are blocked, and I have Flanders, so the isle is cut off. Still, why Scotland?