OK. I will play nicey nice...*sigh* Con, yer friend does have a point, but only to an extent, and to a certain point, and it is very variable.
When i was first bottoming, being penetrated was...odd. It felt good-ish, and hurt a bit (not bad, but there was a very stretched feeling, and depending on angle and length an uncomfortable poking sensation and pressure in certain positions on my badder) and, yes, there were times where it felt as though i had to or wanted to evacuate my bowels of the intruder. It was oart of my bodies way of coping with an unknown feeling. Well Mostly unknown, I had played with toys before, though the same was true of them.
Once my body understood and could quantify the sensation, that feeling of having to take a crap vanished, replaced with only sensations of pleasant fullness, heat, friction, and overall pleasure. I would say it was about 10 times or so of bottoming for various guys before the change was complete. This was for ME though, and there are people who never experience it thus, or always do, or as pain, or any number of ways.
As i said before, I sometimes get that slight sting upon entry. Not always. Not even the majority of the time. Hell not even a quarter of the time.But there are occasions, when I am sufficiently hot and bothered, where I throw caution to the wind, and plow ahead (well I get plowed at any rate, lol) and not just suck up and deal with it, but truly enjoy it.
I hope that clears things up, well from my point of view at any rate.