I think before you give any credance to this article you need to consider the source, personally I think because he holds Christian beliefs he is seeking some justification for his own or his families observance of Halloween and therefore is seeking to conveniently debunk the holiday as being a pagan festival.
The writer suggests the Celts celebrated a 'minor' festival called Samhuinn - the festival was never minor - in my view it is the pagan new year where the veil between the physical world and the spiritual are at their thinnest. His attempt to minimise the pagan element is transparent in my view and is a blatant attempt at self denial. Whilst there is a school of thought that casts some doubt on it actually being considered the celtic new year, it was certainly regarded as 'Summers End' and so therefore again, was never minor. It is also the festival of the last harvest where the fruits of everyones labour was to be stored for the winter and where it was decided what animals would be slaughtered. Ancestors were also honoured at such times, and much divination took/takes place.
In the pagan calendar it is one of the most important times of year as the pagan God is killed to be reborn at Yule - this is also the time where the Goddess goes into mourning and leaves the world in darkness.
Most of the elements of Halloween have their origins in Samhuinn or paganism in general, the costumes, the jack o lantern, apple bobbing and so forth. How anyone can suggest it is of Christian origin is beyond me - especially when Paganism and Pagan Festivals pre date Christianity.
Very poor article in my view - extremely biased, inaccurate and totally misleading!
Gary
