As the others have already said, the system doesn't punish players if they haven't said anything themselves. If you truly said nothing at all to those players, were not arguing with them, or threatening them with reports/bans, then you should send in a ticket to Player Support and ask them to review your situation. It could have simply been a mistake or glitch by the IFS.
However, if you responded to them with the same sorts of comments (i.e. hate speech), or if you were arguing with them throughout the match and have a history of a recent chat restriction on your account, then it's entirely possible that the suspension is justified. Using any form of hate speech, such as homophobic slurs, can result in an account being escalated directly to a 14 day suspension, or even a permanent suspension if it is severe enough. And the standard progression of punishments is 10 game chat restriction, 25 game chat restriction, 14 day suspension, permanent suspension. Even if you did not repeat their slurs and sexist remarks, if you were at the 25 game chat restriction level and spent the entire match arguing with them, that could be cause for moving up to the next punishment level.
Without seeing your logs, it's very hard to guess what may or may not have happened in your situation. I'm not saying that you DID say slurs back at them, or argue with them, simply that these are the sorts of things that we tend to see here on the Boards in similar situations that have led to someone being punished when they were confronted with other toxic individuals. This is the type of situation that Riot designed the mute function for, and in most cases, it can save a person the irritation and offense of dealing with the trolls/toxic players, and prevent them from being punished for whatever retaliation they committed.