Greg was around people who hated him long enough to know when someone was annoyed. Even if he didn't, he knew that his words (or the delivery of them) were enough to annoy the average person. He was never one to be too concerned with the opinion of others, though, which was more than obvious.
He stayed silent long enough to listen to what she was saying, and he was able to put the pieces together... at least, to whatever extent he could. He had no idea what the hell a Voldemort was, but apparently the vision or video she saw involved her fiance dying by its hand. However, she was there... which put a huge flaw in the entire concept of the video. Obviously her fiance was alive when she left so the only way now was for her to go back home, realize that they were in the same house from the video in which a Voldemort could find them in the FIRST place, and she was unprepared to protect herself against it.
But right now, Lily Evans didn't want to hear logic, and in all honesty, Greg didn't want to speak it. He liked watching peoples reaction to everything... he just hated that he wasn't the one pulling the damn strings. These jackasses were having all the fun.
"Well at least you know for a fact that your fiance is alive right NOW, right? Because you're not home. The rest you'll just have to worry about later, because being upset over a fictional video that you saw over the internet isn't going to get you any closer to finding out how to get BACK to your fiance in the first place." She was probably going to tell him to fuck off, and he was prepared for it, but it was true. At this point. If she ever wanted to see her fiance again, dead or NOT, they would all have to focus on the matter at hand or they would be stuck in the hellhole they were stranded in.
"If you just stop and take a breath you'll probably see how unrealistic the story you saw is." He had no idea about the wand, or what it would even mean... all Greg knew what James couldn't have been dead because Lily was here, and if she ever DID go back then she would know what to look for in her surroundings. "Did anyone else experience anything like this?"