Speaking for myself, I was plenty positive when the team was good. I joined this board shortly before our 2010 playoff run and I remember plenty of people bitching about Amare's defense and how we should have traded him and how our bench is overrated and bunch of unwarranted criticism for Jason Richardson as well. I was one of the few people at the time who thougt that we will get it right eventually, whether it was that season itself or the year after (assuming we brought Amare back). I also thought Frye was a perfect fit as a bench 5, pairing him Lou was a match made in heaven due to both of their style of play. RoLo was also someone who I thought would help us big time that year (and he did even though he fell of years after). Many people disagreed with me and thought very lowly of those players. However when went on that 17 or 18 game winning streak, everyone was happy and joyful.
When a team has missed playoffs for 5 consecutive years, it tends to be negative. I see people bashing Suns fans for this, but you should check out boards of other fan bases where their team hasn't had success for 5 years or longer, its just as "negative" or worse. There simply isn't much to celebrate about..yet. Sure Minnesota and Bucks fans are excited about Wiggins and Parker/Ginnis but we don't quite have those type of prospects.
Len and Bledsoe are pretty much our main young guys with a lot of potential and Len has been received with only nice words this season and people are praising Bledsoe more and more as his play improves and becomes more consistent as well.
I'm a Chargers fan and the Chargers have had more success than the Suns in the past 5 years and yet whenever I stop by the Chargers forum, its often doom and gloom as well.
I don't know any forum or any team's fanbase which doesn't react according to its team. I have visited various Suns forums on the internet and I can't say I've seen any that are much more positive or negative than another. You have a team that's a playoff lock, you have fans who are super positive and happy. You have a team that hasn't made playoffs in a while, you have fans who are super negative and unhappy. Its simple human behavior.