Ms. McCall offers some very good points to consider.
I'd also like to add a few points you may want to consider:
Unequal enforcement of workplace policies, including technology and social media policies can create problems for an employer if there are other indications that a termination was based on improper, discriminatory reasons, such as race, religion, disability, etc. But this issue would really need to be discussed with an attorney in your state. I have a few attorney contacts in Texas that I'd be happy to share with you if you want to contact me. Otherwise, Avvo is a good starting place to find attorneys in your state.
For informational purposes, however, I wrote about a case involving an employee who was terminated for social media use (Facebook), but the employee successfully pointed out that other employees engaged in similar conduct. See the link below. Hope this helps and best to you going forward.
Please go to www.shinnlegal.com for more information about my professional experience. But in sum, I'm licensed to practice law in Michigan. My response is provided only to educate the public about general issues that may need to be discussed with competent legal counsel in your state. My response is not a substitute for consulting an attorney in order to fully understand how the law may apply to your specific and unique circumstances; Remember, you often get what you pay for.
So, you're thinking that maybe the best defense is in offense? That doesn't usually work out well in employment law.
The misdeeds of other employees are generally relevant and useful ammunition only if you can demonstrate that the reason that you were treated differently than others who committed the same offense as you did is based on your race, gender, age, religion, etc. Otherwise, employers are generally allowed to evaluate each misbehaving employee individually and to reach a custom-tailored decision as to each.
In many employment circumstances, the issue of misconduct in your situation would be the fact that you were not using your employer's time to serve your employer's interests when you were instead tending your social media presence. Plain fact is, at work you work. At home you play with FB and such. But work is ... work.
My responses to questions on Avvo are never intended as legal advice and must not be relied upon as legal advice. I give legal advice only in the course of an attorney-client relationship. Exchange of information through Avvo's Questions forum does not establish an attorney-client relationship with me. That relationship is established only by individual consultation and execution of a written agreement for legal services.