I don't hate them only for ruining games, often times the game kind of wants to make a balance (Lol) by putting smurfs in both teams, but what bothers me is the attitude of the smurf.
The "don't talk to me trash" kind of attitude like they are so much above everyone else, they will often not play a team game and will not cooperate with the team besides ruining the game for everyone.
They are toxic players who probably don't have much going on in life besides being semi good at a videogame that came out in early 2000s.
Since I play party I will often get matched with a smurf and a guy or a girl who he is boosting. In which case the smurf will be toxic to everyone else but his teammate who is 1 and 9 and is not doing anything on the map. Of course the smurf will then try to win the game on his own while insulting the rest of us and if that fails we are all "trash" and "don't talk to me noobs".
Yesterday I got matched with a smurf in my team and against a smurf in the other team. The other team's smurf was of course much better and was ganking all over the map creating kills while our tried to win on his own by afk farming for 20 min. When that didn't work he gave up mid game while trash talking us on how much better player he is than us and he is looking forward to the next game.
It doesn't make sense for him to waste his energy on a game that is lost, he can boost more efficiently by skipping this one and trying next. His teammate was 1 and 9. Moments ago I got matched with another toxic smurf who died to his mistake and then flamed me for not having a sentry in lane where he died one time. We won the game but I would rather played against that toxic piece of shit than with him.
Source: https://www.reddit.com/r/DotA2/comments/si2ser/why_i_hate_smurfs/