It appears to be a wild accusation to discredit Graham. His accuser (William Gheen) basically seems to say "There have been some rumors in the past that he is gay, and he's voting for stuff I don't like, so obviously he's being pressured to vote that way because he's gay!".
The whole thing seems pretty flimsy in general. The reality is that it's looking like quite a possibility the Graham is likely going to make a run for the presidency next election, and his positions on immigration are unpopular with some in the Republican party, so they're doing their best to discredit him.
It's a shame. Graham is a much more moderate Republican on many issues - but his support on all RKBA issues has been absolutely spot on (he's got an A rating from the NRA). The reality is that we had a HUGE turnout for the last election - and the Democrats won. Trying to win over the ultra-conservatives is preaching to the choir - those people voted Republican last time around to no avail. You have to win over the people who voted Democrat last time around to swing this next election, and a more moderate candidate has a better chance of winning those people over. Yes, I realize that McCain was seen as somewhat of a moderate as well, but you have to realize that we were coming off of the Bush Presidency that soured many people on the Republicans in general. That in itself was going to tip things slightly to the other direction anyways. This time we're coming off of the Obama presidency (hopefully anyways), which is by most accounts much worse than Bush, which means that a lot of people are going to be shifting a bit closer to the Republicans in general. Again though, those people that shift just a little aren't likely to vote for the extremes. By simply looking at a bell curve (which tends to be what most good statistics boil down to) the vast majority of the population is sitting closer to the middle of the road.