This is untrue because most of us weren't born suicidal. We were "normal" once too. I know perfectly well what it was like to "not get it" and think I could never feel this way, but even then I was empathetic and not so callous to those who were...especially not to those close to me. One doesn't have to have first hand experience to give someone else empathy and assume the best over the worst. It's a selfish choice to blame victims and criticism of that behavior is not at all hypocritical.
Only because someone is not suicidal and doesn't know what depression is, doesn't mean that they received in their childhood the entire package of nurture. It's not like they are at the peak of health and any shortage from pure love is them being dicks. People may seem normal and healthy, when they are healthi-er than us. But so many have had their share of neglect as well.
If someone can be empathetic without relating or having experienced the thing themselves, it's because they WERE nurtured a certain way. Others, while seemingly thriving (in comparison to us) cannot empathise at all without relating, and that is because they WEREN'T nurtured a certain way.
Just like when we cannot feel joy or connection or you name it, because we were deprived of something, the lack of compassion in anyone is because they were too deprived of something specific.
So yes they're right to not feel empathy when they just don't feel it. In the same way a depressed person is right to not feel excitement, when they don't feel it.
And it is not fair to declare that they don't love/care. They do it to their limit. (Well, it often happens that they don't, easily seen in comparison with how they treat someone else, about whom they care, the point is to not deduce blindly from one remark) How many people here could be accused of being heartless because they stay grim while a close person is celebrating some achievement? Would you say that you don't care or love that person? You do, but you also have something pushing you down.
At the end of the day, the question is whether you prefer to maintain a relationship with someone with their limitations or not. But blaming anyone for who they are is not only unfair, but also not leading to any change.