Jams are where you go to find out about your playing and have a good time. There is no audience to care about pleasing. So if you friends say you suck they are being jerks, but they went through the same thing maybe even the week before.
I would say take what they said with a grain of salt and learn from the experience. Every time you play is a learning opportunity use it to your advantage, but don't let it stop you. It these guys are to into themselves or thinks jam are suppose to be about parroting a record, find another jam. Just keep pushing. The same stuff goes on at Cut Session (jams for pro's.) Guy trying to get their name known sit in and play, if they play bad they may not be asked to play again for six months. People will say the cat can't cut it. But you go to the woodshed and work and come back and get on that stage again. You will develop a thick skin over time and realize its just part of the game.
As for church don't worry going in and play roots if you have to, it to is a learning ground. These are church players they should act like they are church people give you a chance, and then if doesn't work out then some constructive critism and say come back when you feel you want to give it a go again.
No matter how much you practice at home, no matter how good you are at home, playing with others is totally different. You have to learn to get out and play with other musicians just they way you learn to play bass. Playing with others is another skill to gain and can only be learned by doing it.
