I have huge sympathy for this NCO and think he has been very badly treated by the corps he served loyally. I do not condone his actions, but nor do I condone the actions of a woman suffering from post natal depression who kills her child. The law recognises her condition, hence the offence of infanticide, which is treated differently from murder and often attracts a non-custodial sentence. Sgt Blackman was in an analogous position, and should never been tried for the crime of murder which carries a mandatory life sentence, but manslaughter, for which he could have pleaded guilty on the grounds of diminished responsibility
That said, I understand that anyone still serving should not get involved in this protest, but I also hope that groups like "Britain First" etc do not try and hijack it in order to publicise their own racist views.