Please remove the screencap as you can get in trouble for calling out players on the forum.
Simply submit it with a ticket to support (oh look, convenient link) and explain what happened.
As with many, many, many other people saying these types of things, they are disregardable (I don't think that's actually a word, but you know what I mean), and very reportable. Since pre/post game chat has not been implemented in the report system yet, the screenshot you have is perfect proof to send to Riot.
Also note, that those 2 reports likely won't mean anything against you (if you were innocent), unless you deserved being reported for toxic behavior, of course.