I don't think Marr had much of an influence on Morrissey's views, which had been pretty much shaped much before the formation of The Smiths. But he did shape him musically, as Morrissey's solo work hasn't strayed from The Smiths' mold.
I agree about Linder, and of course the influence of all his favourite authors, musicians, movies etc., but in terms of people who shaped his personality, well, first and foremost, <obvious> his mother </obvious>. The crucial aspects that shaped his character and personality seem to be - his particular (some would say, extreme) attachment to his mother, his closeness to his elder sister and females in general, right from the start (from his aunts to all the girls he made friends with as a teenager), which wasn't typical for a boy of his age and background; and, adversely, the problems and lack of intmacy (according to his account) in his parents' marriage, and their subsequent divorce; his lack of closeness with his father; his secondary school (St Mary's), which was all-male, very violent and very unsuitable for a boy with artistic inclinations; his male teachers and coaches who considered him "effeminate"; the rare (one or two) female teachers who appreciated his poetic streak; and generally, the environment he grew up in, with its strict traditional gender roles, which he didn't fit in. All this contributed to his sense of outsiderdom, his gender/sexuality issues and his rebellion against the traditional notions of masculinity and femininity. It's not hard to see why he would be drawn to 'trans-gender' artists like New York Dolls or Bowie, or to anyone who challenged the status quo.