There is no "Mute" button on TP offer dialogs, mainly because it's rather hard for a griefer to spam you with these. But I guess some hacked viewer or a bot could be used to spam you with TP offers nevertheless.
There are two ways you can already use to work around such spam:
- Mute the avatar manually (View -> Mute List, then "Mute Resident" and fill in their name in the avatar picker).
- Have RestrainedLove enabled and wear an object with that script in it:
I will consider adding a "Mute" button to TP offers...