Uhhh.... 1º of, Steam isn't a Game Engine, but a application to run Valves games (HL Source Engine (HL2), most actual mods of HL1 and some new games that that joined Steam).
Anyway, great friends you have there -_-
Perhaps you should aproach with a diferent talk with them, for exemple:
"Let's try to make a fun game with FPSC, not a BIG SUPA UBER 1337 game, jsut a fun small one."
This way they can't really "flame" you, becouse of the graphics and this and that.
Also, if they start "flaming" why making a game in FPSC engine, you can answer:
"Becouse we don't need a UBER 1337 engine to make a game that we enjoy playing for some hours, also, how many of us are here to make teh game? Also, we don't have 20years of exeprience like the ones at Valve, Midway, EA, etc."
"Also, how many game engines are out there to make FPS? We have lots and i really mean lot's of engines to make RPG games, and almsot none to make 3d ones, much less to make a FPS."
I really hate when people comes with *censured* comments about the stuff we make for FREE for them, specially our friends :/
Ohh well, what can we do?
Just don't listen to them and get other ppl that enjoy our work
We have billions of players out there looking for this type of work, some are willing to pay for it, others, not, but at least we know that we'll always have someone that will like our work.
My love is seperated in 2 parts, 1 of them is 3ds Max 7, the other; FPSC.