Security can take many forms from magnetometers to security clearances or a combination of measures. I believe supporters will submit security clearances/background checks in order to have access to rallies. People want to be heard. They will come to free rallies and have confidence if they qualify for invitations.
Pop-up rallies at fairs and spontaneous gatherings may have their own sense of fun as well as security. Advertised rallies probably carry higher opportunity for violence.
It is unfortunate the level of violence we are facing, but, it is nothing the Democrats have propagated. Liberal gun laws are embraced by Republicans. They have created their own hell. Democrats and their voters need to protect from it while enjoying the rallies they seek.
Democrats have suffered enough over the years from political violence and the threat of it. The voters have to realize there is a far different security paradigm now if we are going to be able to elect qualified people to end the political hatred propagated by Trump. The escalation of danger has to end. People will embrace safety measures.
Rallies must be secure from the hatred raids by Trump and ICE.