I noticed the other post by by-tor and easymo and i'm not referring to this incident because I know nothing about it and from my experience with both of them..this is just a "fog of war" thing.
In an H2H Session:
Unsportsmanlike conduct (lol sounds like hockey..) is easy to deal with.
-Make sure everyone know the host rules.
-Simply warn and ultimately boot the offender.
It is also possible to log and ultimately ban specific I.P. adresses from ever joining your host. (mega-squelch

)
Just use a firewall like the free Zone Alarm.
I have noticed some hosts use their name in the session name. This helps me decide if the session is one that is "managed" correctly.
(arena settings and type of "attitude")
The host makes a big difference in the session IMO. After a while you get to know who the hosts, you find worthwhile to join are, especially if they post their ID in the host name.
In the MA:
This would be harder to manage. It's up to the community and HTC to minimize this.
But Hey... I can't justifiably comment on this more since I can't afford to fly in the MA at present.

Regards,
Snoopi