These people are doing dangerous things.
these people do not do dangerous things
The people doing dangerous things are not the same people who do no do dangerous things.
exists e1 s1 x1 x2.(n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_thing(x2) & a_dangerous(s1) & Theme(s1,x2))
exists x1.(n_people(x1) & -exists e1 s1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_thing(x2) & a_dangerous(s1) & Theme(s1,x2)))