finger printing and photo are standard practice for EVERYONE except US citizens, canadians, and certain visa classifications. even green card holders get printed and photo, every time they cross. primary and secondary questioning are also standard practice.
and it IS their business what you do outside our shores. they can ask you anything they want to determine your admissability to the US, including what you do for a living, where you have been and why, and purpose of your travels. it's nothing personal, they are just being vigilant and doing their jobs. if you have recurring in-depth interviews with patdowns and all that, they should provide you with a comment card and tear sheet so you can write and inquire to the goverment and they will answer any questions you may have, and might even fix the problem for future travels.