This is a very valid question and a common request. Quite a rational one. Most penalties for chat infractions are most effective when the person knows what they did. Blizzard’s template software used to include at least some snippets of the conversations that were reported, or were near the reports. That way there was something to remind a person of what might have been discussed during that time frame.
Problem was, it broke at some point and was not linking the correct logs through their player template tools. The GMs could see it, but I guess they were not given permission to manually copy over quotes. That would take a lot of individual time.
As a result, a lot of Support contacts are generated because people don’t know what a GM penalized. Many players are frustrated and it causes a lot of extra tickets and appeals vs just telling folks what they said.
Blizzard knows that, and I think the plans are to fix the tools that let them insert or attach chat transcripts into the email templates.
Also, remember that something does not have to be “offensive” to be inappropriate for the game. Be nice to folks you don’t know, just like you would in mixed company around any strangers. Save colorful taunts, trash talk, jokes for private chat with friends who share those preferences.