I think those marines are stupid. How can they let blackbeard do whatever he want to do? Why they still want to capture luffy who already passed out but do not stop blackbeard who can destroy the marinford??

The only reason why the let Blackbeard do as he pleases is because they want the Marines to have all the Warlords of the Sea available and ready to go so that they look strong. They also let him do so because he caught Ace

I think Blackbeard is a bigger threat to marine.

However, if we see the past record between Luffy & Blackbeard, of course Luffy would be marine 1st target

Remember: Defeat of 2 warlords (Crocodile & Moria), Enies Lobby, Impel Down + he is the son of the revolutionary Dragon

wew ==a

i think its because they just saw blackbeard absorb whitebeard's power and at that time it was 'whibeard's age' so they were too terrified to raise a hand against blackbeard, on the other hand luffy is Dragon's son, has less power than blackbeard and the marines have faced luffy many times to know that they have a high chance of capturing luffy
this is only my personal opinion though