Only name that comes to mind is Blaž Kraljević. He was leader of Croatian Defence Forces (HOS), a paramilitary force serving under Bosnian Armed forces. He did better than arguing against extremism, he stood up against extremism. The only condition he presented to hard-pressed-on-all-sides Bosnians for his cooperation was that Bosnia will remain a sovreign country and would not surrender to Serbia.
He was an outspoken advocate of Bosniak-Croat alliance and vehement opponent of Croat and Serbian attempts of dividing Bosnia. He denounced both self-proclaimed Croat and Serb Republics in Bosnia.
His force was diverse that consisted of 5,000 volunteers including Bosnian Croats, Bosniaks, and foreigners.
The attitude of this force can be summed up by words of their previous patron and later rival, the Croatian Defense Minister Gojko Šušak when he proclaimed that Croatian Defense force was actually Muslim Defense force.
Kraljević explained his mission as:
I'm here to protect these people, and I'll do it or die trying. We are
not a Catholic army because 30 or 40 percent of the ranks of HOS is
Muslim. We are the army of Bosnia and Herzegovina. Personally, I would
like to see Croatia to the Drina, but who will decide that is the
people here, the people of Bosnia, when the war ends. In regards to
HSP and HOS, all those who are not extremists and have not bloodied
their hands can stay and live here and we will protect them. We will
protect the Serbs and Bosniaks and Croats from any external enemy,
because we are behind the people. In regards to external opinions
about us, including their interests, the interests of Germany or the
United Kingdom for us here are utterly irrelevant, because I only care
for the people here.
The Statement in Bold implies that there had been extremist and criminal members among the ranks of the HOS however no allegation of war-crimes on the commander himself says he did what he could.
When Bosnian-Serb and Croatian leaders met in Graz to reach an agreement about Bosnia's future, He pleaded to his people:
We implore all citizens of Bosnia and Herzegovina, especially Croats
and Bosniaks, not to take into account any statements or agreements
between Mate Boban and Radovan Karadžić. Neither speaks in the name of
Croats and Bosniaks. They do not represent what the Croats and
Bosniaks want. ... HOS and the TO are defending, and will defend,
Bosnia and Herzegovina.
There is no charge of war-crimes or any atrocity against him and he served his people well until he was murdered by HVO possibly on behest of Croatian Government. After his death, Croatian media ran an eloborate campaign to discredit him however later in 1996 Croatia awarded him Order of Petar Zrinski and Fran Krsto Frankopan posthumously.