I don't think people should be canceled for expressing opinions, but that's not the same as funding an effort to actively harm people. He is entitled to his opinions, but he is not entitled to enforce them on other people.
Anyway, there isn't any proof that Eich hates gay people in the way you imply. He didn't lead any anti-LGBT changes at Mozilla and there haven't been any at Brave. The commentary is that he did one thing that really offended a bunch of people. There just aren't compelling reasons to think he's a monster.
In 2008 when Proposition 8 was on the ballot, that Eich privately supported, even President Obama (candidate at the time) was publicly against gay marriage.
There needs to be some historical cultural context, supporting Prop 8 in 2008 is different than supporting Prop 8 in 2023. Now if Eich said he would support it in 2023, that's a different matter.
But I would still use Brave browser and search since it's a good product.
If I accepted that agreeing with the majority makes everything okay, I couldn't criticize the many horridly immoral things the majority still agree with today.
I still use Brave sometimes, and I would probably still use it if he did the same thing today, but I will continue to think he is a bad person unless he at least donates the same amount (adjusted for inflation) to a charity that supports LGBTQ+ people.