it seems as if the democrats are acting as provocateurs, trying to instigate a physical confrontation that they cannot win in the physical arena but can use as an excuse to impeach trump for contempt of congress.
it seems to me that trump has the option of offering to send a military armed escort along with each witness to congress. if congress declines this, then trump would in theory be off the hook.
trump could also cite executive privilege.
trump could also claim that impeachment hearings have not started yet due to lack of a full house vote (maybe try this option first).
the witnesses could perhaps take the 5th (how would this play with dual jurisdiction, i wonder, if the response were to grant federal immunity).
all of these could end up in court (in which case the danger may be from john roberts).
I believe the letter Trump sent a few days ago stated this.
The house has already voted down impeachment twice. This contrived “whistleblower” complaint was used as an excuse for Nancy Pelosi to announce that an impeachment inquiry was going forward, but there has been no vote supporting it, only Nancy’s decision to go forward.
From the timeline, it looks as though certain DemocRATs pulled this scheme together when the last impeachment vote failed. Maybe they were hoping to create a narrative, then hold another vote. Unfortunately for them, President Trump immediately declassified the phone call, showing that the “whistleblower” complaint was a total fabrication.