Hi Matthias,
Not sure how to do this in NetSight natively, but there may be an alternative you can do on the switches:
To exclude netlogin user logout traps from being sent to NMS:
conf snmpv3 add mib-view defaultnetofyview subtree 1.3.6.1.4.1.1916.4.3.0.5 type exclude
To prevent netlogin user login traps from being sent to NMS:
conf snmpv3 add mib-view defaultnetofyview subtree 1.3.6.1.4.1.1916.4.3.0.4 type exclude
You would need to push these 2 commands to each switch using NetSight or another script.
Regards
Tony