On Tuesday, four Olympics athletes from United States showed up at Beijing airport with masks  over their mouths and noses. Though they thought it was just a simple “precautionary measure” against the pollution in China, such behaviors were interpreted much differently by the Chinese internet users.
The No. 1 accusation is that the masks  were intended to embarrass Chinese as a protest with political implication.
Blogger Gass-rooter(草根情怀） railed against  them
The U.S athletes finally put on their masks to China, the black masks, as ugly as gas masks…. The conceit way they wore them disgust us Chinese……
Don’t slight these little black masks. The U.S has planned to do so, to embarrass China in the presence of the world, though slef-proclaiming that they were just taking care of the athletes’ lungs.
Firstly, when U.S hosted the Olympics in Los Angles, whose air pollution was even worse than Beijing’s, they did nothing. But this time they just could not get along well with the air condition in Beijing.
And he furthermore took people living in Beijing as arguments.
Secondly, not mentioning the dense population in whole China, just in Beijing are so many people there, and we are all living fine and with joy day after day. Why the hell have they got to put on masks once they arrive?
He finally concluded the mask as a sign of insulation. “Why do we have to withstand it?” he questioned.
Compared to this lengthy redicule, some just commented in short words with anger :
F**k off! ******
More people thought the athletes impolite.
afhel  said:
They were impolite to China, at least to Beijing. It’s just like shaking hands with you with gloves on, which implied you are felt dirty.
不一定1 in Tianya said :
You are guests that come to the home of a host who tidy up his room and welcome you warmheartedly. And shouldn’t you show friendship and kindness at the point? Even if there is a few aspects to improve at the house, shouldn’t you show understanding and toleration?
In senses of these net users, wearing mask is but a chilly rejection to Chinese courtesy, a behavior that “give no face to Chinese”, as translated from the Chinese idiom, 不给面子.
And 誓佐 ‘s comment  gave another reason explaining why they feel pissed off by the athletes:
For Olympics, for clean air, we nationals almost have to clog our assholes to let no gas out, but the Americans just don’t give you face (give you respect).
This grief is in some way justifiable. To prepare Olympics with good air, over 100 factories were shut down, and in Beijing, over 2 million vehicles  were banned to run on way per day, industrial production and transportation affected. Also, the strict security measures in many cities bring abut great inconvenience.
That’s why some suggested it’s a ceremony to flatter the foreigners by the price of the citizens’ regular life; looking on the troublesome 2008 more or less associated with Olympics, it probably makes sense.
Back to the topic, however, there is also voice at the other side no less resonant than the aforementioned.
露珠湿纱壁 relentlessly contradicted the internet users who scolds the athletes:
You have the right to call their names, but so that they can freely wear masks.
Brainwashed too much by CCP, you’ll of course feel piqued for your master, even if it doesn't need you to. What a wretched nation!
On August 6, the U.S athletes concerned, under the pressure of U.S.O.C. officials who were apparently unhappy with their choice (according to New York Times), apologized . The 4 cyclists said it was in no way meant to serve as an environmental or political statement.
On this apology, many Chinese internet users felt it a victory, while still a few thought it not a sincere one. But meanwhile some felt sorry with Chinese.
骑着蚂蚁猎大象 said: 
That people should apologize because they wear masks indeed shows that China is 5 times better than some place. (It alludes to an embassy’s statement that the human right condition in China is 5 times better than that of U.S —- translator)
By the way, are masks sold in China? I suggested the masks being banned tomorrow, and punishing all those put it on.
Wear or not to wear masks, might not be a question for the guests, but the host, a sensitive host.
What a great country is it supposed to be that even cannot stand a man with mask?
（Additional:less than 30 minutes to the Olympics. Regardless of so many controversies, may the ceremony be blessed!)