Yeah I've heard Xtians say that about tattoos - they also say that about piercings. I have a lot of piercings.
I like the look myself : )
What normal person would insult a stranger??
The old lady probably had an emotional reaction to your tattoos, and simply made up an argument to fit her sentiment. From her point of view, your appearance was disgusting. You offended her first. And she is right.
I think I read a survey that 50% of the population find tattoos revolting. So, statistically you are going to disgust half the population if you display your tattoos in public. It's nothing to do with atheism, it's an emotional reaction.
Listen to what the person's heart is saying, not what their words are.