OMG.

Post the paper they gave you with the alignment numbers after each alignment.

They have them on file if you failed to ask for them. Have them fax it to you or scan it and email it. It is your right to have these.

The dealer is (1) stupid, or (2) liar with the nonsense about sandbags. Yes, some BMW procedures says 'load the car prior to alignment' BUT THIS WILL NOT CAUSE A BAD ALIGNMENT. If the SA doesnt know this he is stupid, if he does know this he is purposefully being evasive or misleading.

The truth is that the "BMW Spec" is quite large and can yield 30,000 mile tire life or 8,000 mile life- all being "in spec"

I've posted on this 100 times. Search.