Because boys are raised by their opposite sex parent,they must put
rigid boundaries between themselves and their mothers in order to
define themselves as masculine.If the boy's mother is emotionally
expressive and his father is not,then emotions are experienced as
feminine and they threaten masculine identification. When the boy
feels something, he becomes anxious about his masculinity and learns
to deny and devalue feelings.What do you think?

Dear Moti, 

There is a dominant theory that an anti-femininity norm lays at the
heart of the emotional expression of the men, or rather, the lack of
them.

However, in modern families, this could be disputed, and the origins
of restrictive emotionality could be associated with previous life
experiences (Snell, W. E., Jr., Belk, S., & Hawkins, R. C. II. 
(2001).  Chapter 8:  The masculine role as a moderator of
stress-distress relationships.  In W. E. Snell, Jr. (Ed.),  New
directions in the psychology of gender roles:  Research and theory.
Cape Girardeau, MO: Snell Publications. WEB:
<http://cstl-cla.semo.edu/snell/books/gender/gender.htm>) and not only
those associated with home rules, but with the rest of the society -
socialisation processes that include the nursery schools ("boys don't
cry"), the youth clubs ("this is a girlie game/toy", "don't run like a
girl"), and ending with workplace, further education and other means
of socialisation.

Gender role conflict, thus, could, but does not have to be, related to
parental emotional legacy. Moreover, another explanation altogether
could arise: when the parents are emotionally cold (whether it is the
father or the mother), the boy does not learn how to express his
emotions effectively, and has a conflict that is not only connected
with his gender role, but also with his relationships with his
parents.

I hope that answered your question. In order to answer it, I used my
own knowledge and analysis (after all, you asked for my opinion, "What
do you think?"), but also searched the Internet
<://www.google.com/search?num=50&hl=en&lr=&ie=UTF-8&oe=UTF-8&q=%22Restrictive+Emotionality%22&sa=N&tab=gw>.
If you need any clarifications on this answer before you rate/tip it,
let me know and I'll clarify.

Hi moti-ga...

I cannot agree with your question on restrictive emotionality. I
raised my son  on my own from birth to present ( he is now 27 yrs old
). I am the *mom* and to this day, my son has never questioned his
masculinity or any denial of feelings. He has grown into a wonderful
young man with whom I have the pleasure of calling "my friend"
now...no dad ws ever in the picture...

I've known several men who grew up with emotionally effusive mothers
and stone-faced fathers. I don't notice any "devaluing of feelings" in
these men. If anything, they seem more comfortable with emotional
expression than other men.