intuition.
symmetry.
rewrite <-(@evalDist_right_ident _ eqd).
comp_skip.
simpl.
repeat match goal with
|- context [ if ?X then _ else _ ] => destruct X
end; rewrite ?@eqb_leibniz in *; reflexivity || congruence.
Qed.

Theorem Prob_or_indep_le :
forall (c1 c2 : Comp bool),
Pr[b1 <-$ c1; b2 <-$ c2; ret (b1 || b2)] <= Pr[c1] + Pr[c2].