Hi Newbie,
What would make sense for the character?
Is he a coward?
Does your character dare not attack him because he'll get snotted?
How much of this is out of game issues between you and the other player?
If there are no external issues and your guy is a bit of a coward, then he'll make excuses, look to stand behind others and do his best to say why he's useful to the party. Hopefully, other party members will come to your defence and pull the big guy into line. If your character fails to have support, he'll skulk about tail between legs for a little while and if things don't improve, he'll leave the party hanging when they need him most.
However, from your tone, it seems that there are external issues. If so, you'll need to sought it out with the DM and the Player as Crothian suggested - a definite font of wisdom Crothian is.
Best Regards
Herremann the Wise