Simon Trask is the brother of Bolivar Trask but was a more outright villainous individual who did not appear to have the interest of humanity at heart (though he may well believe that he does).
Brother of the late Bolivar Trask, Simon Trask hates mutants even more than his brother, but unlike his brother, he didn't consider the Sentinels to be the right means to oppose the "mutant menace". Instead, he started a fanatic anti-mutant movement called Humanity's Last Stand, and rallied baseline humans into joining the ranks of his ever growing organization. Simon Trask didn't stop there, though, he tried to stir up anti-mutant hysteria by creating a fake Mutant Liberation Front that performed acts of mutant terrorism. Actually though, the members of the group were Trask's own followers wearing technological armors that mimicked mutant powers. These efforts were stopped by the Punisher and the X-Cutioner. Simon Trask seemingly died when he blew up his own base, trying to become a martyr for his cause.
Following M-Day and the events of Messiah Complex, the X-Men relocated their base to San Francisco. Among the first opponents the faced was Simon Trask, now leader of the Humanity Now! coalition who leaked to the press the decimation of Cooperstown, Alaska, blaming mutants for the damage caused by the Marauders and Purifiers. He announced the creation of Proposition X, a mandate that would require all mutants to subject to birth control procedures, stating that the birth of a new mutant child will bring disaster.
Unfortunately, despite positive thinking that Proposition X would never be formed, it did. Trask and his followers came to San Francisco to demand that all mutants subject to the proposal. Immediately, riots began breaking out, between pro-mutant and anti-mutant activists. Trask was initially injured, but once he was recovering in a hospital, he began to infect everyone he touches with what looks like a techno-organic strain. It caused his victims to transform into a biomechanical Sentinels, intent on eradicating mutants, good, evil or even government sponsored. However, his entire legion was decimated by the Dark X-Men and Trask was arrested.
However, Trask's action lead to the X-Men establishing an independent nation out of the former Asteroid M.