How can I present a persuasive argument as to whether the employee leave granted by the Family and Medical Leave Act (FMLA) represents an undue burden on employers required to comply with the act?

The act requires that employers grant employees job-protected and unpaid leave for qualified medical and family reasons. Qualified medical and family reasons include personal or family illness, family military leave, pregnancy, adoption, or the foster care placement of a child.
Your argument should consider the following points:
Would the employer suffer any serious financial losses if leave is granted?
Does job-protection for an employee mean a loss in working hours and thus affect production, or may the employer hire a replacement for the period concerned?
How do restrictions on employees who need to take leave benefit the employer? Or are they a disadvantage to the employer?
The following post should help:

The FMLA was intended "to balance the demands of the workplace with the needs of families." The Act allows eligible employees to take up to 12 work weeks of unpaid leave during any 12-month period to attend to the serious health condition of the employee, parent, spouse or child, or for pregnancy or care of a newborn child, or for adoption or foster care of a child. In order to be eligible for FMLA leave, an employee must have been at the business at least 12 months, and worked at least 1,250 hours over the past 12 months, and work at a location where the company employs 50 or more employees within 75 miles. The FMLA covers both public- and private-sector employees, but certain categories of employees are excluded, including elected officials and their personal staff members.

Remember, the focal point of your argument is "undue burden." Define this in your introduction and thesis statement. Your argument should be supported by strong statements either in support or against the topic. Since your word limit is quite restricted, you need to be succinct and to the point. Use the detail provided in the above post for support. The following guidelines should also help:
Take a strong stance on the topic in your thesis statement
Use plain and direct topic sentences to begin each paragraph. 
Use short sentences.
Be authoritative and sound like an expert.
Use persuasive techniques such as repetition and validation. One or two well-placed rhetorical questions in such a short piece can also work.
A brief conclusion which reiterates your thesis statement should bring an effective end to your piece.
https://en.wikipedia.org/wiki/Family_and_Medical_Leave_Act_of_1993