Ok, we've all been there, we had some player who wasn't very good at all who was clearly dragging the team down, what do you say to that guy? I mean, for example I just had a heimer who went 1 and 8 in my last match, he constantly needed 3 people bot and we couldn't gain any ground because of that, he whined about being 2v1'd but in reality he was dying solo to ryze mostly, all I said was that bot lane shouldn't constantly need help and that it was out of control.

The guy flips out and tells me to shut up and stop being abusive to my teammates, after that I actually did trash the guy, the usual "don't play X champion anymore" stuff, I find myself doing this a lot, it usually starts with me saying that someone isn't being very helpful to the team, and that alone makes people extremely angry, so what do you guys say in that situation? I can't just say nothing, nothing will be accomplished that way

When you can pinpoint a specific mistake they make, point it out. Common mistakes include not building resistances or penetration when necessary, so suggest their next item to build for them.

Sometimes people just have an off game, or get outplayed, and there's nothing to do, and nothing that needs to be said.

Personally, I'd have tried to get him to switch to top, or tried to gank bot till it snowballs back in his favour. I think Heimer's stronger top lane anyway.

Also, you lose all points for "After that I actually did trash the guy."
Doesn't matter what happens, that's uncalled for. Dude knows he's doing bad, at some point you're just badgering him. "Bot lane shouldn't constantly need help" isn't constructive in any way, it doesn't give him anything to work with.

Say something constructive.
Do something constructive.
Or shut up.

"it usually starts with me saying that someone isn't being very helpful to the team"
This statement isn't very helpful to your team either, is it? You also noted it happens to you a lot. Maybe the issue is with you?

More about shutting up:
" I can't just say nothing, nothing will be accomplished that way"
You're accomplishing not making things worse.

what i do is introduce them to a champion called teemo, then i suggest building a blackfire torch.

" OH ****, WHAT THE **** ARE YOU DOING? STOP DIVING THE TURRET LIKE THAT. OMG IM THE BEST IN NA WHY DO I GET MATCHED UP WITH YOU? WHY, MATCHMAKING WHY? STOP BUILDING RYLAI'S ON JAX, WHAT THE ****. REFUND ALL YOUR CHAMPIONS AND UNINSTALL THE GAME. AND PLEASE, IF YOU EVER QUEUE UP AGAIN, PLUG IN YOUR MOUSE BEFOREHAND. "

and then i end up 9001-0 and carry the game

Actions speak louder than words - help out with ganks and pings, backcap when the enemy isn't guarding...do whatever you can to carry the match!

merkenberry, why are you going around the Dom forums trying to tell people to play BFT Teemo? Are you trying to prevent it from getting nerfed? If so, it's already nerfed for the next patch, it's been confirmed by a RiotNome and several of us have seen it on the PBE too. If BFT Teemo really is the love of your life, I recommend finding a new love, because BFT is getting nerfed, and live team thinks Teemo's Poison is on the strong side, especially since BFT and Liandra's Torment are on the PBE now. In other words, Teemo is getting nerfhammered.

The solution is that yes, you can just say nothing. It's as simple as that.

If you can't phrase your criticism in a way that isn't constructive, as in "Hey, can you just play safe and defend tower until we can come help", just ping or stay silent. You could have also tried to get a lane swap to occur like "If bot lane isn't working for you, can someone else (or you!) take over bot?"

What you can do gameplay is ping, gank bottom, and instantly leave for top once you've ganked. People in Dominion have a tendency to follow whoever they think has some sort of idea what they're doing - in the case of ganking bot sometimes that helps and sometimes it doesn't. Liberal use of pings can hopefully help with that.

I change the subject and talk about my favourite K-pop band - Girl's Generation to pass the remaining 10-15 minutes of the game while playing passively bot lane.

Nothing.