If your girlfriend / boyfriend kissing a same gender people , is that cheating ?

Now now , i always so curious that why when a straight girl and straight girl kiss ,it  can be perfectly fine .

( photo credits to en.wikipedia.org )

I mean , guy will say "it's so hot" . But i got 1 question to all the guys , if you saw your girlfriend kissing another girl , will you consider that as a cheating ? What will you do or react ? 

But you see , when a straight guy kiss another straight guy .

( Photo credit to roccosrevolution.com )

Girl and guy both will say " eww , that's so disgusting , that's so gay " . Why so gender bias ? Here's my question to all the girl , if you saw your boyfriend kissing another guy , will you consider that as a cheating ? What will you do or react ? 

Note : I do respect lesbian , gay and bisexual people . This post is meant for straight guys and straight girls . 

Do remember to leave your comment ya . 

Thanks for reading ! 

Bye!