Why do you think it is A OR B instead of A AND B?
It's the way it's worded.
802(5) is the preamble to the section which ends with the expression "that--". This leads into 802(5)(A). Run (A) and (B) together, as an experiment. The grammer does not place (B) after (A), but as a seperate thought, as in "... that-- appear to be intended--".
802(5)(B) is subdivided within itself as (i), (ii), and (iii).
If it was intended to be (A) and/or (B), it should have been written like this (using your text - I trust you copied it correctly):
"...(5) the term `domestic terrorism' means activities that-- `(A) involve acts dangerous to human life that are a violation of the criminal laws of the United States or of any State, and/or; `(B) appear to be intended-- `(i) to intimidate or coerce a civilian population; `(ii) to influence the policy of a government by intimidation or coercion; or `(iii) to affect the conduct of a government by mass destruction, assassination, or kidnapping; and"
Without that little and/or bit, (A) is a thought, seperate and apart from (B).