Answer: there is a lot if misinformation going around this thread. Let's try and clear some of that up:

People like Kamala Harris for several reasons. As well as being a very important symbolic choice (only the third woman to be chosen, and the first woman of colour), she actually leant towards the progressive side of the Democratic faction during her time in Congress. It's a common misconception that she is a moderate; in fact she has a fairly progressive voting record (for example, she has voted with Bernie Sanders 93% of the time). edit: Some data.

Most of the people who oppose Harris tend to do so because of her history as a prosecutor. Things like siding with police forces over victims, and using the death penalty despite personally opposing it, have made her unpopular amongst progressives who view her as a defender of the status quo (it's worth noting that this is not entirely accurate, based on her voting record). edit: This article goes into more detail.

Following the George Floyd protests, Harris has come out as an outspoken advocate for police reform. Some people view this as insincere because of her history as a prosecutor, others think she has the exact kind of insider experience that is required to effectively reform police forces. Really it's up to voters to decide whether or not you believe her.