First of all, no one's saying that 2 men can't have a close relationship without being gay together. God there are a million pairs of friends in media that are certainly bromantic, in a platonic sense. Look at Sherlock and Watson, Kirk and Spock, Sam and Frodo. Those guys are not in love, they're all friends. Erik and Charles are different.
I think you're misunderstanding why they would put this pair in a relationship. Shock value has absolutely nothing, nothing, NOTHING to do with it and I'm bewildered by that accusation. Throughout their stories in the comics and cartoons, there has been SOMETHING there. A deep connection, sometimes hinted at romantic, sometimes as just good friends. But it's always there. Their connection is so deep that whether you interpret it as platonic or not, it's really not that big a stretch to assume they could also have feelings for each other. I'm not talking about sex, I get the impression that they've never done anything physical with each other. It's not about sex, it's about intimacy and ~~feelings~~. In ALL of the movies, you can feel them longing to be together on the same side. XMFC just made clearer the reasons why.
And again, as I quoted from that fanperspective, the timeline kind of backs it up. Like the author said, this relationship taking place over years and ending with such heartbreak and betrayal? Brotherly bromance. This relationship taking place over 6 months and reacting like that? Something was going on. For someone like Erik who TNO, he gets attached to Charles rather quickly. Charles can see Erik's whole life, but vice-versa isn't an option available to Erik. But he trusts him implicitly anyway, in such a short time. Something more is going on. It add SO much more depth to their relationship. Friends is one thing but if they went through this whole half-year with this kind of expectation that once Shaw was done with they could address whatever it was they were feeling and be together, only for it to end in every way they didn't want it to, it's that much more tragic. Erik has not planned his life beyond Shaw, Shaw has always been the number one goal in his mind, the only goal. I imagine he'd have been just as satisfied to die as to live as long as he got his revenge. But then Charles came in, and while he still took a very very farbackseat to Shaw, I imagine that Erik stopped thinking about life post-Shaw being irrelevant.
TLDR, I actually think the idea of Charles and Erik with ~~feelings~~ gives their characters MORE depth because it shows just how much they mean to each other on levels neither one thought they could feel for someone else (much less a man). Shock value really isn't a reason they would do it. If they wanted SV they'd have had much more success following comics and giving Raven a girlfriend and knocking her up by morphing into a man. but Fox is still a Family Values company on many levels, sadly. So in the meantime all we get is subtext.