I explained to him that both of these persons could not use mumble because alt+tabbing out of their current game could cause a game-crash. I further explained that the two individuals were in ventrilo with me (the demo and heavy, I was medic) so I could relay the information between the two VOIP clients.
I shouldn't really be posting here as this is not a disucssion forum but your friends in vent could have quite easily joined the mumble first before joining the game, I do this quite frequently as alt+tabbing out of the game can take a while even in windowed mode and can cause my desktop to bug out. Also it's not a case of you relaying the information to them it's them being able to quickly relay information to the rest of the team, heavy and especially demoman are very important classes in HL as they are 2/3 of the main combo along with the medic. They have to be in mumble in order for it to be a balanced lobby otherwise the team with those classes in mumble will most likely have a much easier time.
New players are intimidated with the lobby/competitive system (please, look up the above referenced lobby players) and the hostility expressed above has turned these players away. Personally, I have introduced about six members to the lobby/TF2Center universe within the past week. Unfortunately, this experience has turned these newer players away because these issues aren't relevant to the contrary TF2 experience: Pubs!
TF2C do their best to try and make their site as inviting as possible to newer users. Having said that, you and your friends chose to join a mumble required lobby rather than a non-mumble required lobby and you chose not to open mumble before TF2 and so you chose to inconveniance your team, I'm sure OP will have been totally fine with your friends closing the game and then booting up mumble and then reopening TF2. I know this because I have to do it myself sometimes if the mumble overlay is not working.
Honestly I think you and your friends could have handled this a lot better and I would suggest that perhaps the site is off putting because you aren't using it correctly. Also whilst mumble server communication is not important in pubs it is the entire point of comp TF2. The major difference between comp TF2 and "pub" TF2 as you put it is that it is organised and organised solely through the use of mumble. If your friends are not willing or able to do this then comp TF2 is not for them and TF2C can't really help them with this aside from offering non-mumble required lobbies as it's rather implicit in the format of comp TF2.
Edited by R.E.M., 20 August 2014 - 02:27 PM.