what about the christians and jews and hindus and buddhists and athiests that have done lots of killings too?
I don't think it's true to say these are not reported. However, the key difference is the
reason for the killings. Usually they are not killing in the name of religion. Or to put it another way, there are 'killers who are Christian', but not so many 'Christian killers'. Their religion doesn't get mentioned because it's not relevant (and quite possibly not known).
why don't have anything good to say about islam at all?
In the UK and Ireland I have seen plenty of coverage suggesting a positive side to Islam. But it isn't the strongest discourse for two reasons.
Firstly, there are constant new incidents of violence by people who say they are acting in the name of Islam (whether or not you regard them as Muslims doesn't matter, that's how they identify themselves and their objectives, so it has to be reported). To make it worse, in many cases there is an associated link between becoming 'more Muslim' (eg praying more, breaking off contact with western friends because they think they are immoral) and becoming more violently inclined.
Secondly, moderate Muslims themselves seem to be fighting a losing battle within Islam. If this were happening within Christianity, there would undoubtedly be a big debate going on within the Church and much soul searching about the faith and the direction it was taking. That does not seem to be happening within Islam. Or is it happening but we're not seeing it?
Instead of that, there is a terrific debate about perceived western antagonism. Worse still, there is also a very strong minority (perhaps a majority?) who have constructed an elaborate conspiracy theory around events that effectively means all Muslims are innocent and all westerners are guilty. There is no possibility of compromise and understanding if this view spreads too far.
For both Muslims and non Muslims, there seems to be a difficulty in separating the religion from the man. If a man plants a bomb in the name of Islam, he gets referred to as an 'Islamic terrorist'.
Unfortunately, many Muslims read that as a statement that Islam itself means terrorism (which it does not say). Muslims regard Islam as the ideal religion, something incapable of any flaw. So they reject the criticism. As a result, from a western point of view, it looks like Muslims are 'defending' the terrorists or at the very least refusing to condemn them, which is terrifically damaging to the image of Muslims and of Islam.
why do they always say muslims always kill innocent non-muslims
The vast majority of terrorist incidents in the world right now are Muslim on Muslim - in Iraq, Pakistan and Afghanistan. There are so many that only the worst incidents get coverage, but people are aware of the constant background of violence. This too contributes to the negative image.