i heard about this on the news. i don't have any specific info/logic to use to counter the claim that thimerosal is safe. i just use my common sense on this. thimerosal contains mercury. mercury is toxic. so the odds that thimerosal are "safe" to me are just not very high. when thimerosal is spilled in a lab, lab workers must take hazardous materials precautions in cleaning it up: gloves, masks, etc. so why would it NOT be a bad idea to inject it into a child?
this kind of argument (like the CDC's here) always kills me because it's just asking you to overlook common sense. it's like those arguments that organic food is worse for you than conventionally grown food (yes, people argue this)--or at best equal. it's just common freaking sense that ingesting chemicals and toxins is best avoided.
i don't know how else to put it

to me, asking for evidence of why thimerosal in vaxes is bad is like asking for evidence of why you shouldn't use gasoline as a salad dressing.