If he wishes to convey that, he can write "I am angry." But I would advise against that.
Because there is another point, that one should be aware of. There is a huge "power differential" between the sender and the recipient of the mail.
If I were to say "Puff_Of_Hot_Air posts a lot of cr*p online" this might not be nice, but it would not impact his life much (but perhaps our relationship). Our levels of "power" are roughly same.
Should I write the same about an employee of my company, this might make that person fear for his job. That is because in that context, I wield a lot of power. The effect is there, even if I do not intend to do any harm.
Linus is a very powerful person. Not formalized power, but probably more powerful than the average politician. Others may socially or otherwise harm the person dissed in that post. Not because Linus wants it to be done, but just because those persons admire Linus. There are probably a lot of admirers in the area the recipient is working in.
The excessive use of such explicit language will lower the barrier that prevents others from taking a negative action.ï