That's not true at all in my experience. Both as a manager to others, I've always tried to be loyal to employees who invested in the employer/employee relationship - and as an employee who benefitted from having an employer/managers look out for me when inevitable bumps in the road occurred in my personal life.

Outside of my own direct experience, I can also recall many other co-workers' experiences where the companies I've worked for went above and beyond in their commitment to their employees. One time that meant making many extraordinary allowances for an employee suffering from a mental breakdown. At times it has meant extending the employment of someone who was looking for a life/career change, but the company kept on paying a salary until the employee found somewhere new to land - way beyond where the employment had any real benefit to the company. There are many others.

By all means, takes some precautions. By all means, stand up for yourself. By all means, make sure that you're being fairly compensated... but if you go into every relationship, personal or business, with your shields raised and phasers set to kill - you will reap what you sow.