If I had team members who were struggling and other team members who were not and who were finished their own work, I too would expect those devs to help. The deadline and the work comes first, period.

You don't have time to be on SO as much as you are because the work is not getting done. It is as simple as that. If the work was getting done, he wouldn't be upset. The work is not my tasks and their tasks, it is our tasks. You rearrange workload to get the work done and that is what he is doing. It appears to me that you are not committed to your job since your rep on Stack overflow is apparently more important to you than what you are being paid to do. That is a problem and one I would not be happy about as a team lead.

If I had team members who were struggling and other team members who were not and who were finished their own work, I too would expect those developers to help. The deadline and the work comes first, period.

You don't have time to be on Stack Overflow as much as you are because the work is not getting done. It is as simple as that. If the work was getting done, he wouldn't be upset. The work is not my tasks and their tasks, it is our tasks. You rearrange workload to get the work done and that is what he is doing. It appears to me that you are not committed to your job since your reputation on Stack Overflow is apparently more important to you than what you are being paid to do. That is a problem and one I would not be happy about as a team lead.