Well, I won't support flaming, so there's that.
I want to stand on the gameplay perspective of people thinking playing safe is ok. Sometimes it is, most of the times it's not. I hate myself when I see the argument "I'm playing safe and just farming". The game isn't about trying to outcs your enemy laner or maybe get a kill lead over them. There's so much more, from laning pressure, to map pressure and map control and warding, to which playing safe doesn't attribute a lot. It's one thing to play safe when you're the easiest to gank lane and already behind, and another to just be under tower and farming and pretty much not interacting with your enemy, not pressuring and not helping your team.
What I really hate is how people go like "but I called SS and now you gave the enemy Zed 2 kills by roaming bot", while they do nothing to pressure them mid lane and dissuade them from safe roaming without giving up minions and tower damage. "I was outcsing them and also had a kill over them (with jungle assistance, of course) and now the enemy has 3 kills, REPORT MY TEAM". Typical bronzie argument who thinks everything revolves around outcsing and outkilling the enemy.
Not, to your particular game, I can't say whether it was safe for you to play the way you did, but generally, with a lead like the one you say you had, and with a champion like Lissandra who can very easily assist in ganks and kills, playing more around the map to help your team would be a more ideal approach.