Yes. That. Hartley would certainly know what it was like, the assumptions, but in a more direct and immediate sense as he couldn't exactly... fix what had happened to him. And unintentional as those results might have been, there wasn't really anything that he could say that would make the situation better. He could hardly change the outcome.
"I didn't realize you were going to be affected so severely," Eobard said, frowning to himself. "Granted, none of the side effects other than Barry's were planned. I knew there was going to be fallout. But you, Ronnie, Cisco. None of that was intentional. Simply a regretful side effect to a necessary evil."
But there was no sense in apologizing for something he couldn't change.
As Hartley turned away from him, though, his attention seemingly diverted to anything that wasn't him, Eobard stepped away from the door, crossing over to Hartley and settling a hand lightly on the young man's shoulder, "Because if I cared, and still did what I did, it's just further proof that you, yourself, are not enough to overcome the other issues people might have that get in the way of loving you?"
It was a low blow, perhaps, but it was the closest possible thing to what Hartley might be thinking that Eobard could come up with. After all, someone could only get rejected by the people they loved so many times before they ended up taking it to heart as some sort of personal defect or failing.