It’s getting ugly out there on social media. Anti-vaccine activists are attacking pediatricians head to head on Twitter, Facebook and other social media platforms, and they’re not hesitating to make their attacks personal. A few fed-up doctors are fighting back, both online and, more recently, in the courts. One pediatrician, Dr. Eve Switzer of Enid, Oklahoma, filed a defamation suit last year against former Oklahoma ophthalmologist Jim Meehan and Oklahomans for Vaccine and Health Choice, saying they publicly and falsely accused her of failing to provide informed consent to parents about vaccinations. “Anti-vaxxers have gotten out of control,” Switzer told NBC News. “As a pediatrician, the way that it has affected me personally, my practice and my staff, even, I really felt like I needed to have some sort of remedy and my only remedy was a legal remedy.” Anti-vaccine groups are getting more confrontational on social media. Many Facebook groups, such as this one, are outright saying they oppose all vaccination of children despite overwhelming scientific proof about the benefits of vaccination. It's difficult enough to counter the continual questions raised by vaccine skeptics and activists who, increasingly, say all vaccines are unsafe for all children. Worries about autism, a preservative called thimerosal, the spacing of vaccines, vaccine ingredients and whether kids get too many vaccines have all been repeatedly and thoroughly addressed, but that doesn’t stop users of social media from bringing them up again and again. “Going up against the anti-vaccine movement is a thankless task for a number of reasons. For one, the goalpost is moving,” said Dr. Peter Hotez, director of the Texas Children's Hospital Center for Vaccine Development and dean of the school of tropical medicine at Baylor College of Medicine. “So if you can explain why MMR (measles, mumps and rubella) vaccine doesn’t cause autism, they’ll turn around and say well it must be thimerosal in vaccines. If you debunk this, then they’ll say ‘well we are spacing vaccines too close together’ and if you debunk that and then it’s aluminum in vaccines,” he added. “I call it the global health whack-a-mole.”