On first reading it seems like, as if it doesn't make sense.
'Just as long as you stand by me ....'
Think of people who are completely absorbed in their own thoughts when they are in trouble. That's what the singer is afraid of. He won't shed a tear and won't be afraid as long as the other person stands by him. But what if his lover/confidant has any problems of his/her own? Will he/she then be able to protect me?
I'd use 'stand by someone' figuratively. However, support may also include financial or physical help.





