Why don't they share with you that the polls they are conducting that show Hillary in the lead are do to the population they poll being primarily Democrat which is not representative of our country?
Because what you are saying has no basis in objective reality. Here is how the pollsters determine who is a Independent or not: They ask and people self-report.
Now, all pollsters have house effective which means they tend to order a number higher or lower than the true value. But the reputable polls themselves track each other pretty closely. They all move about the same amount in the same directions. That's why poll aggregators like fivethirtyeight, Drew Linzer, Princeton Election consortium, etc. predicted the 2012 election very accurately, in some cases completely accurately, down to the last electoral vote. The simply look at lots of polls, and the errors within each poll tend to cancel each other out.
Interestingly, in 2012 we were hearing the exact same complaints as you are making. Romney was having huge rallies, polls not counting independents, the polls must skewed, etc. But when the election results were counted, the polls provided an eerie level of accuracy. With that caveat that most polls
under-counted support for Obama.
Here we are just four years later, and people are claiming the exact same things that were wrong last time. I'll go ahead and step out on a limb: I'll say that Clinton will win the election by 339 electoral votes, to Trump's 199 EV, plus or minus 15. Plus I'll say that the Democrats will win the Senate (50 seats or more).
And a general comment: The news media should try to be objective, as much as anyone can be. That is their obligation to the public. But deciding not to report non-sense is being objective.