Mistakes happen (you accidentally taking their blue). And it sounds like it might be the fault of the jungler. Either way, what I usually do is offer to then immediately leash red. It usually helps to calm the jungler down and let them know it was unintentional. I'll do this even if it sets my lane back.
(on the off-chance you also subsequently steal red, well... I've got nothing for you LOL)
As far as punishment being harsher, I think the punishment system is right where it needs to be. The 'detection system', on the other hand, could be better. People who intentionally feed often go multiple games until they are reported/detected/discovered. Yet, I don't have a solution, and until someone finds a better method to what exists I'm don't forsee this changing.
As for their flame, I presume you didn't flame back and reported them after the game for verbal abuse and for griefing/inting. Being specific in your reports is always a good idea, on the off chance that said report gets reviewed by a flesh and blood human being. Also, remember you don't have to deal with their verbal toxicity - you can mute the offending players, or the entire board if necessary.
Finally, if you did nothign wrong you have nothing to worry about from multiple reports. It doesn't matter if you are reported by 1 or 9 players, if you didn't break any behavioral rules during the match it won't count against you.
Good luck man, don't let the jerks get to you. See you on the rift (or more likely the Abyss, as that is where I spend a lot of my time).