I don't think I'd ever reach that conclusion based on someone's self-reporting. Too prone to bias.

So what would convince me? Well, the same way MLK convinced me: actions. Not in the sense of having to lead a civil rights movement, but rather in the sense of displaying that level of love and compassion when there is a cost to doing so. Are you so committed that you'd risk imprisonment or assassination? There's really no way for me to tell unless real life tests your mettle. I admit, it's a high bar. Extraordinary claims require extraordinary evidence.

How then would I gauge the love and compassion of someone who had to hazard neither life nor liberty? I have on occasion witnessed people perform generous acts which would not have even occurred to me, but upon seeing them I could not doubt their rectitude. More common is just a general pattern of behavior: how an individual interacts with others.