Boris Johnson: Parliament doesn't want Brexit.
Jo Swinson: I won't back a Corbyn-led Labour government.
Corbyn supporters: LibDems won't back Labour.
Same "false generalisation from the specific" fallacy, just from different angles.
In LDs case, they might yet back Labour led by a different better leader, just not the rubbish one they have been offered so far.
The instinctive reaction to being attacked is to dig your heels in.
And then we're stuck.