As I said in my OP there is no issue with second accounts. The issue comes in when the person artificially tries to keep their account elo low by throwing matches or not performing for the sole purpose of continuing to play versus low elo players.
Smurfs arent just people with secondary accounts. They are people who go all out one match and then play poorly in the next couple matches. This allows them to feel like they are good players, when the reality is they are just gaming the match maker so they can just beat up on players far below their skill level.
Its the gaming the match maker I don't think that should be legal.
For reference. I was in a match for a few rounds with an admitted smurf. One of the games I was on his team, he ran around with nothing but the classic head shotting people. He went 18/15. Respectable, sure, but then the next round, I guess he was salty I called him a scum bag smurfer, so decided to go all out. He ended the match 28/5. This is where the issue comes.
If he played at his full skill consistently the match maker hopefully would place him with players closer to his skill level.