Honestly, I think they've been very foolish about this in the past. Door to door knockers and Convention attendees have been sitting ducks for whatever nut case they happened to encounter.
Either way, these heightened security measures will be more fodder for their "end times" predictions. "See how bad things are getting friends? Jehovah's people have to be cautious as serpents yet innocent as doves"
The irony of it is, most of them believe they are Jehovah's chosen people and will say that he is protecting them yet on some level they know it's not true, hence the need for these security measures. It's the same sort of reasoning that lets them preach that the end of the system is upon us yet go ahead build a new billion dollar headquarters, claiming they'll need it after Armageddon, even though every factory, resort, hotel, warehouse and home on the planet would be theirs for the taking, afterward.