Yes, she was speeding and yes, she should have signed the ticket. But still: it's hard to watch a cop shove and tase an elderly woman. But she wasn't totally subservient; and so she got the treatment. More details at Pam's House Blend:
Remember: you're in America. As the Boston cop put it, the woman made a fatal error:
assuming she has rights when considered a suspect.
If they'll tase an old white woman to the ground, and arrest and tase a mentally disabled deaf man, or cuff someone for simply speaking his mind, be aware. We're all criminals now.