www.farsinet.com/cyrus/ Toabdalwali, other people have given Universal Human Rights, including racial
and religious rights centuries before Mohammed, like King Cyrus of Iran, gave his subjects equal racial and religious rights, and
banned slavery a millennia before Prophet Mohammed's birth. Buddha lived in a pretty race ridden society, where the White skinned Aryans despised the dark skinned Dravidians, and called them lower castes, and he too proclaimed equal rights for all. Of course, he was prepared to give up his life for a lamb, rather than slaughter those who didn't adopt his faith like lambs.For that matter, Jesus too spoke against tribalism in his Parable of the Good Samaritan more than half a millennia prior to Mohammed, and literate Christians like Waraqa might have known this parable(I'm
not accusing Mohammed of learning it from him though). So these stuff had been said and done before,and by people who didn't physically destroy other faiths.
As for racial discrimination being worse than religious discrimination, according to me what matters isn't whether the condition is alterable, but how painful is the discrimination from those suffering due to it. For a lot of people their faith truly matters, and the idols of their gods\esses are more precious than life itself. The Zoroastrians who fled to India, the Meccan who fought wars to protect their idols were all devoted to their faith. A lot of Muslims I know identify themselves as Muslims first and by their country later, and the same holds true for many people of other faiths.Changing faith, teaching a new faith to their kids, witnessing destruction of the physical images of their gods is extremely painful for them, and they'd fight for it with their lives, just like they'd fight racial and gender discrimination.
As to why the Meccans persecuted Mohammed even when he was peaceful at the beginning, the best people to answer that would be the Meccans themselves. From the Meccans own behaviour, we know that they happily tolerated conversion to Christianity, like Waraqa's case shows, and also recognized the Jewish principle of religioous lineage coming from the mother, as you yourself have stated. Why would such people suddenly become intolerant? My hypothesis is that they probably realised the danger this man and his faith posed to their ways of life, and his intention to forcibly interfere with and destroy their faith as soon as he achieved the ability to do so. Before the hejira, Mohammed didn't get enough converts to wage a war for his cause,
and military or physical weakness shouldn't be mistaken for genuine peacefulness. Avowed revolutionaries and radicals also bide their time, until they achieve the ability to bring the change they seek.
In any case, the Meccans' fears proved correct, as Mohammed not only got the rights for his followers to pray at the kaaba, he also destroyed the Meccans cherished idols, calling them falsehoods, and threatened to kill anyone who came out to defend them.The Scandinavian nations for eg are pretty tolerant, you can preach any faith, and convert anyone, but if they suspected that a faith would destroy their ancient Lutheran churches as soon as it got the military capabilities to do so, would they allow it to remain?