Sometimes game terminology can be sensitive or offensive to certain people even if it isn't meant in a harmful way. If a player is harassing you and telling you to get cancer or literally wishing that you get cancer then I completely agree that this is unsportsmanlike behavior and should be reported. However, if a player says that a champion is cancer because of their cheese or cc or ability to steamroll and dominate then that is not harassment, and neither is calling a team composition cancerous because every single time they catch someone or pick someone off their health is instantly deleted.
There is a difference between player harassment and harmless game terminology that is meant to be humorous, and it appears that what you are describing is a sensitivity to terminology that is not intended to be harmful. I hope that explaining the difference helps, but if you are being harassed then definitely use the report feature!!