Studies have shown that viewers are
less likely to remember commercials in violent TV
shows than in non-violent ones. I suspect that it generalises to anything
that induces excitement (tension/release) and altered states in the viewers
impairing retention of advertisements. Though stating it as "violent" programs
having this commercially harmful effect may be a political move, to persuade
marketers that the War On Violence is good business rather than a potential
loss of revenues.