Maybe they are scared that he would have influence over the market. It is possible that people are concerned that if he successfully acquires a large amount of Bitcoin he would have influence thereby having the capacity to manipulate the market.
Others might be jealous of his success. The amount of Bitcoin Michael Saylor has acquired within a short period can attract haters.
1.8% of bitcoin's total supply, which the company holds already, is enough to put fear in people's bodies even if they don't accumulate more, which we all know they still are not ready to stop.
They will still be able to make some shakes in the market, because just an announcement of saying, "We will likely sell off some of our holdings on a certain date," that alone without any action can put the market in panic mode, but that's not something people should be worried about.
The company is busy doing what they know will work well for them; those hating are busy doing their things, and at the end of the day, there will be only one winner and many losers.