tendentious- Marked by a strong implicit point of view; partisan: a tendentious account of the recent elections.
I have no problem at all if you say that Coulter has a strong point of view; those who do not, simply don't understand the situation.But the "implicit" part of the definition goes to the point that a "tendentious argument" always is concealing its agenda. Just like The New York Times would have you think that it's a bastion of nothing-but-the-facts truthtelling when in fact its "facts"--lately is some disrepute--have been carefully selected to avoid helping Republicans with too much inconvenient truth.
The article could have said "opinionated", and gotten away with it. But "tendentious" is always a perjorative.