Straight up - everyone is different. Sadly, a lot of inexperienced (and ignorant ones) seem to think only porn stars and promiscuous girls are 'capable' of swallowing, like it's some sort of skill. Personally, I think it's less mess to clean up and swallow out of a sense of ease - plus my man enjoys it, so win-win. That said, I've totally just not felt like it on occasion and just spat it out or, in especially funny situations, ended up half-choking and coughing it all up anyway, which thankfully we got a sense of humour about so we can laugh about it when it happens.
Basically, if a guy is shook you swallowed, he's not been near many women before and needs to get over himself. Sounds like he's got some very immature ideas.