Well, I am not usually sympathetic to Republic senators.
But I think I remember that it was already fairly obvious before Burr's stock sales - seeing what had happened in China - that we were going to have a serious pandemic. So I am not entirely sure what Burr learnt in the meeting that made it impossible for him to sell his stock.
Obviously if material, non-public information was shared, that is a thing. But if it was just an economic opinion that things were going to get bad, I'm not sure how that would have made the stock sales illegal.