your post says a lot about you as a father (no, i didnt say step father).
when in lfd, whether i'm a tank or a healer or a dps, someone always has something to say. tonight i was tanking the final encounter, had my camera all the way zoomed out and was trying to click on the tentacle to taunt. well, since my back was to the claw, and since the claw is so huge, wherever i clicked, it was the claw. needless to say, the person closest to the tentacle died (it was the noob 7k hps healer, lol) by the time i was in tab target range to taunt it. the healer then went on to absolutely berate the tanks, how we didn't know the fights, should be kicked, etc. when the tentacle died i br'd him, buffed him and when we were on the claw i said, even though there are 2 tanks, "my bad, i had my camera zoomed out and clicking the tentacle only clicked on the claw" - i took the blame even though it was his stupid idea to be all the way back there, and was closest when it spawned even though i was already omw to the area but couldn't click it.
anyway, this all is meant to show you and your son that by default, everyone in the world is first to blame, last to learn. you and he are doing everything right by the sounds of it, and have to put up with the 99% crap people you will lfd with.
sometimes kicks are warranted though. i ran the same lfd THREE TIMES tonight in order to complete it. we kicked "healers" who were dps'ing full time, dps'ers who weren't even beating the tanks in single-target encounters, and dps'ers who were sub-10k. there's just no excuse for any of that. oh, and the people who were in stormwind the whole time. wow.
keep on keepin' on, and explain to him that people simply don't know what they're doing. i've been kicked from 5mans before while tanking (i have 4 380+ tanks lol, and have tanked since 2004, i know what i'm doing...usually ) and have had people leave the pug, create a toon on my realm, and send me a tell saying that they kicked me by mistake, that they meant to kick someone else, and apologize. it comes down to learning/knowing your class, learning the fights, and doing the best you can. everyone makes stupid mistakes (my dbm bars covered "the button" on a few encounters initially, and couldn't click it, oops!) and others even try sabotaging (dps picking up the healing crystals "cuz they can"...) the raid. knowing that you're doing what you should be doing defeats anyone's misguided insults, even if you get kicked or have to /ignore someone.